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Bureau of Mines Information Circular/1987 



Cost Estimation Handbook 
for Small Placer Mines 



By Scott A. Stebbins 







UNITED STATES DEPARTMENT OF THE INTERIOR 




Information Circular 9170 



Cost Estimation Handbook 
for Small Placer Mines 



By Scott A. Stebbins 






UNITED STATES DEPARTMENT OF THE INTERIOR 
Donald Paul Hodel, Secretary 

BUREAU OF MINES 

David S. Brown, Acting Director 



As the Nation's principal conservation agency, the Department of the Interior has 
responsibility for most of our nationally owned public lands and natural resources. This 
includes fostering the wisest use of our land and water resources, protecting our fish 
and wildlife, preserving the environment and cultural values of our national parks and 
historical places, and providing for the enjoyment of life through outdoor recreation. 
The Department assesses our energy and mineral resources and works to assure that 
their development is in the best interests of all our people. The Department also has 
a major responsibility for American Indian reservation communities and for people who 
live in island territories under U.S. administration. 

IN 235 



.11* 

no. 1)70 




Library of Congress Cataloging-in-Publication Data 



Stebbins, Scott A. 

Cost estimation handbook for small placer mines. 



(Information circular / Bureau of Mines; 9170) 

Includes bibliographies. 

Supt. of Docs, no.: I 28.27: 9170 



1. Hydraulic mining— Costs. I. Title. II. Series: 

Information circular (United States. Bureau of Mines); 9170. 



TN295.U4 [TN421] 622 s [622 '.32] 87-600145 



For sale by the Superintendent of Documents. U.S Government Printing Office 
Washington, DC 20402 



CONTENTS 



Abstract 1 

Introduction 2 

Acknowledgments 2 

Section 1.— Placer Mine Design 

Exploration 3 

Panning 4 

Churn drilling 4 

Bucket drilling 4 

Rotary drilling 5 

Trenching 5 

Seismic surveys 5 

Mining 5 

Backhoes (hydraulic excavators) 6 

Bulldozers 6 

Draglines 6 

Dredges 6 

Front-end loaders 7 

Rear-dump trucks 7 

Scrapers 7 

Processing 7 

Conveyors 8 

Feed hoppers 8 

Jig concentrators 8 

Sluices 8 

Spiral concentrators 9 

Table concentrators 9 

Trommels 9 

Vibrating screens 10 

Sample mill design 10 

Supplemental systems 13 

Buildings 13 

Camp facilities 13 

General services and lost time 13 

Generators 13 

Pumps 14 

Settling ponds 14 

Environment 14 

Cost estimation 15 

Cost equations 15 

Cost date adjustments 15 

Site adjustment factors 16 

Labor rates 17 

Financial analysis 18 

Bibliography 18 

Section 2.— Cost Estimation 

Capital and operating cost categories 19 

Capital costs 20 

Exploration 20 

Panning 21 

Churn drilling 21 

Bucket drilling 21 

Trenching 21 

General reconnaissance 21 

Camp costs 21 

Seismic surveying (refraction) 21 

Rotary drilling 21 

Helicopter rental 21 

Development 22 

Access roads 22 

Clearing 23 



Page 

Preproduction overburden removal 24 

Bulldozers 24 

Draglines 25 

Front-end loaders 26 

Rear-dump trucks 27 

Scrapers 28 

Mine equipment 29 

Backhoes 29 

Bulldozers 30 

Draglines 31 

Front-end loaders 32 

Rear-dump trucks 33 

Scrapers 34 

Processing equipment 35 

Conveyors 35 

Feed hoppers 36 

Jig concentrators 37 

Sluices 38 

Spiral concentrators 39 

Table concentrators 40 

Trommels 41 

Vibrating screens 42 

Supplemental 43 

Buildings 43 

Employee housing 44 

Generators 45 

Pumps 46 

Settling ponds 47 

Operating costs 48 

Overburden removal 48 

Bulldozers 48 

Draglines 49 

Front-end loaders 50 

Rear-dump trucks 51 

Scrapers 52 

Mining 53 

Backhoes 53 

Bulldozers 54 

Draglines 55 

Front-end loaders 56 

Rear-dump trucks 57 

Scrapers 58 

Processing 59 

Conveyors 59 

Feed hoppers 60 

Jig concentrators 61 

Sluices 62 

Spiral concentrators 63 

Table concentrators 64 

Tailings removal 65 

Bulldozers 65 

Draglines 66 

Front-end loaders 67 

Rear-dump trucks 68 

Scrapers 69 

Trommels 70 

Vibrating screens 71 

Supplemental 72 

Employee housing 72 

Generators 73 

Lost time and general services 74 

Pumps 75 

Bibliography 78 

Appendix.— Example of cost estimate 79 



ILLUSTRATIONS 

Page 

1. Sample flow sheet, sluice mill 10 

2. Sample flow sheet, jig mill 11 

3. Sample flow sheet, table mill 12 

4. Exploration cost summary form 21 

5. Capital cost summary form 76 

6. Operating cost summary form 77 

A-l. Sample flow sheet 80 

A-2. Capital cost summary form completed for example estimation 87 

A-3. Operating cost summary form completed for example estimation 94 

TABLES 

1. Sample material balance, sluice mill 10 

2. Sample material balance, jig mill 10 

3. Sample material balance, table mill 10 

4. Cost date indexes 17 





UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 


BCY 


bank cubic yard 


LCY/h 


loose cubic yard per 


d/a 


day per year 




hour 


ft 


foot 


pm 


micrometer 


ft 2 


square foot 






ft 2 /yd 3 


square foot per 


min 


minute 




cubic yard 


min/h 


minute per hour 


ft/h 


foot per hour 






gpm 


gallon per minute 


St 


short ton 


h 


hour 


st/h 


short ton per hour 


h/shift 


hour per shift 


tr oz 


troy ounce 


hp 


horsepower 


tr oz/yd 3 


troy ounce per cubic 


in 


inch 




yard 


kW 


kilowatt 


wt % 


weight percent 


kW/yd 3 


kilowatt per cubic 


yd/h 


yard per hour 




yard 


yd 3 


cubic yard 


lb/LCY 


pound per loose cubic 


yd 3 /d 


cubic yard per day 




yard 


yd 3 /ft 2 


cubic yard per 


lb/yd 


pound per yard 




square foot 


lb/yd 3 


pound per cubic yard 


yd 3 /h 


cubic yard per hour 


LCY 


loose cubic yard 


yr 


year 


LCY/a 


loose cubic yard per 
year 







COST ESTIMATION HANDBOOK FOR SMALL PLACER MINES 



By Scott A. Stebbins 1 



ABSTRACT 

This Bureau of Mines publication presents a method for estimating capital and operating costs 
associated with the exploration, mining, and processing of placer deposits. To ensure represent- 
ative cost estimates, operational parameters for placering equipment and basic principles of placer 
mining techniques are detailed. 

Mining engineer. Western Field Operations Center. Bureau of Mines. Spokane, WA. 



INTRODUCTION 



In 1974, the Bureau of Mines began a systematic assess- 
ment of U.S. mineral supplies under its Minerals Avail- 
ability Program (MAP). To aid in this program, a technique 
was developed to estimate capital and operating costs 
associated with various mining methods. This technique, 
developed under a Bureau contract by STRAAM Engineers, 
Inc., was completed in 1975, then updated in 1983. During 
the course of the update, it was noted that few provisions 
were made for estimating the costs of small-scale mining 
and milling methods typically associated with placer min- 
ing. The popularity and widespread use of placer mining 
methods indicated that a cost estimating system for placer 
mining would be of value to prospectors, miners, investors, 
and government evaluators. 

This report has been written to aid those involved with 
placer mining in the estimation of costs to recover valuable 
minerals from placer deposits. It relies on the principle that 
cost estimates will be representative only if calculated for 
technically feasible mining operations. Because the design 
of such an operation can be difficult, provisions have been 
made to assist the user in achieving this goal. 

Section 1 of the report describes the processes involved 
in placering, and may be used to aid in designing a viable 
mine. Operational parameters for equipment commonly 
used in placer exploration, mining, and processing are 
discussed, as well as basic principles of successful placer 



mining techniques. If the reader is unfamiliar with this 
form of mining, section 1 should be thoroughly understood 
prior to estimating costs. 

Section 2 contains cost equations that enable the user 
to estimate capital and operating costs of specific placer 
techniques. Cost equations are designed to handle the wide 
variety of conditions commonly found in placer deposits. 
This allows the reader to tailor estimates to the 
characteristics of a particular deposit, which ensures 
representative costs. Although based primarily on gold 
placer operations, cost equations are valid for any other com- 
modity found in deposits of unconsolidated material. Equa- 
tions are geared to operations handling between 20 and 500 
LCY/h of material (pay gravel plus overburden). Estimated 
costs are representative of operations in the western United 
States and Alaska, and are based on a cost date of January 
1985. 

The appendix provides an example of placer mine design 
and cost estimation using the information contained in this 
report. 

This report is not intended to be an exhaustive discus- 
sion of placer mining. Many detailed texts have been writ- 
ten on this process, any one of which will assist the reader 
in method design. A number of these are listed in the 
bibliographies accompanying sections 1 and 2. 



ACKNOWLEDGMENTS 



A special debt is owed to the late George D. Gale, 
metallurgist, Bureau of Mines. This handbook, and many 



of the ideas and facts it contains, are the product of his 
ingenuity. 



SECTION 1.— PLACER MINE DESIGN 



The complete design of a placer mine involves the in- 
tegration of exploration, mining, processing, and sup- 
plemental systems for the efficient recovery of valuable 
minerals from an alluvial deposit. This design is the first 
step in accurate cost estimation. 

In this section, individual systems are categorized as 
follows: 

1. Exploration.— The phase of the operation in which 
resources are delineated. Because the amount of time and 
effort spent on discovery is difficult to tie to any one specific 
deposit, only the processes of delineation and definition are 
costed. Field reconnaissance, drilling, and panning are 
representative of items in this category. 

2. Mining.— Deposit development, material excavation 
and transportation, and feeding of the mill are all in- 
cluded in this category. Items such as clearing and over- 
burden removal are also included. 

3. Processing.— Processing is defined as all tasks required 
to separate the desired mineral products from valueless 
material. 

4. Supplemental.— Any items not directly related to 
mineral recovery, but necessary for the operation of the 
mine. These might include buildings, employee housing, 
and settling pond construction. 

Before designing a placer mining operation, the 
evaluator will need information concerning the deposit 
under evaluation. Preliminary information helpful in ex- 
ploration program, mine, mill, and supplemental function 
design includes 

1 . Description of deposit access. 

2 . Anticipated exploration and deposit definition 
requirements. 

3 . An estimate of deposit geometry and volume. 
4 . Distribution and location of valuable minerals 
within the deposit. 



5 . Geologic characteristics, volume and depth of 
overburden. 

6 . Depth, profile, and geologic characteristics of 
bedrock. 

7 . Local topography. 

8 . Physical characteristics and geologic nature of 
valuable minerals. 

9 . Availability of water. 

10. Availability of power. 

11. Environmental considerations. 

12. Labor availability and local wage scales. 

13. Housing or camp requirements. 

Information should be as detailed as possible. By pro- 
viding such items as exact haul distances and gradients, 
accurate estimates of overburden thickness and deposit 
area, the evaluator will increase the precision of cost 
calculations. 

With the preceding information in hand and the help 
of the material contained in the following pages, the user 
will be able to design a technically feasible operation. The 
following sections will assist the evaluator in planning each 
phase of the mine. When designing systems for individual 
areas of operation, the evaluator must keep in mind that 
these systems will interact and must be compatible. For in- 
stance, hourly capacity of pay gravel excavation should 
equal mill feed rate, and the mill must be set up to easily 
accept gravel from the equipment used for material 
transportation. 

Most of the information contained in the following pages 
is based on average operating parameters and performance 
data for the various types of equipment used in placer min- 
ing. Costs and conclusions derived from this manual must 
be considered estimates only. Because of the many variables 
peculiar to individual deposits, the stated levels of equip- 
ment performance and costs may not be realized on any 
given job. 



EXPLORATION 



It can be safely stated that far more people seek placer 
deposits than actually mine them. Exploration for placer 
gold can be enjoyable work and has achieved a recreational 
status in the western United States. For the serious miner, 
however, exploration is only the initial phase of a complete 
mining operation. Consequently, it incurs a cost that must 
be repaid by the recovery of valuable minerals. 

For the purposes of this report, exploration is divided 
into two phases. The first phase involves locating the 
deposit, and the second consists of defining enough of a 
resource to either justify development or to eliminate the 
deposit from further consideration. 

Costs for the first phase of exploration are difficult to 
attribute to any one deposit. This type of exploration is 
typically regional in nature and deposit specifics are 
rarely considered. For cost estimation purposes, expenses 
associated with a specific deposit are the main concern. Only 
costs directly related to the definition of that particular 
deposit will be calculated. Accordingly, this discussion deals 
mainly with the deposit definition phase of exploration. 



Time, effort, and money spent on resource definition 
vary greatly from one deposit to the next. Some miners are 
satisfied with the degree of certainty obtainable with shovel, 
pan, and physical labor. Others, wishing more security, 
systematically trench or drill the deposit and process 
samples using some sort of mechanical concentrator. Still 
others, hoping for greater assurance, follow up drilling or 
trenching by bulk sampling using machinery intended for 
mining. These samples are then processed in a scaled-down 
version of the proposed mill. The extent of effort spent on 
deposit definition is related to 

1. Degree of certainty desired. 

2. Availability of capital. 

3. Experience of the operator. 

4. Historical continuity of similar or local deposits. 

It is intuitively obvious that the degree of certainty of 
success is related to the extent of exploration undertaken, 
and it is desirable to delineate the deposit as extensively 
as is practical prior to production. In many cases, however, 
lack of exploration capital and the need for cash-flow limit 



the exploration phase, and mining commences on the 
limited information at hand. Goals of a thorough explora- 
tion program include determination of 

1. Deposit volume. 

2. Deposit and overburden geometry. 

3. Deposit grade. 

4. Distribution of valuable minerals within the 
deposit. 

5. Geological and physical characteristics of the 
valuable minerals. 

6. Geological and physical characteristics of waste 
material. 

7. Location, geology, and physical nature of the 
bedrock. 

8. Water availability. 

9. Environmental concerns. 

Much of the information needed to estimate costs of 
developing and operating a placer mine is gathered during 
deposit exploration. Consequently, costs estimated after ex- 
ploration are much more precise than estimates made prior 
to exploration. 

In section 2 of this report, two methods are presented 
for estimating exploration costs. With the first, a cost can 
be calculated by simply estimating the total resource of the 
deposit. This method is based on total exploration expen- 
ditures for several active placer operations, but is not con- 
sidered as precise as the second method. 

The second method requires that the evaluator design 
an exploration plan. This plan should include the type and 
extent of each exploration method required, for example 

1. General reconnaissance, 5 days with a two-person 
crew. 

2. Seismic surveying, 10,000 linear ft. 

3. Churn drilling, 4,000 ft. 

4. Trenching, 1,000 yd 3 . 

5. Samples panned, 2,000. 

6. Camp facilities, four people for 20 days. 

To aid in developing this plan, some techniques com- 
monly employed for sampling and subsurface testing of 
placer deposits are discussed in the following paragraphs. 
These include panning, churn drilling, bucket drilling, 
rotary drilling, trenching, and seismic surveying. 



waste during production. Skilled use of a gold pan during 
the mining sequence can make or break the small mining 
operation. 



CHURN DRILLING 

Methods of drilling placer deposits are quite varied, but 
the most common technique is churn drilling. Typically, the 
churn drill uses percussion to drive casing down through 
the material being sampled (in some instances, casing is 
not used). After a length of casing is driven, the contents 
are recovered (bailed), another length of casing is added, 
and the process is repeated. Depths are usually restricted 
to less than 150 ft, and hole diameters range from 4 to 10 in. 

One advantage of this method is that sample process- 
ing keeps pace with drilling, allowing good control of drill- 
hole depth and instantaneous logging. A churn drill is 
generally operated by two people; the driller operates the 
drill, bails the sample, and keeps track of the depth of each 
run; the panner estimates the volume of the samples, pans 
them as they are recovered, and logs the hole. 

Drilling rates average about 2 ft/h but can reach as 
much as 4 ft/h in clay, soil, sand, pebbles and soft bedrock. 
The machine is suitable for drilling through cemented 
gravels and permafrost, although productivity will 
diminish. Penetration is drastically reduced in ground con- 
taining boulders and in competent or hard bedrock. 

Samples recovered from churn drill casings are often 
subject to volume changes caused by compaction or expan- 
sion of material within the casing. Sample volume changes 
can also be caused by compaction around the bit forcing 
material out into the surrounding formation, and by 
material "run-in" due to high deposit water content. One 
or more of these conditions may be encountered in any one 
deposit, requiring the application of volume corrections. 
This task is often difficult and requires the experience of 
a qualified driller or engineer. 



BUCKET DRILLING 



PANNING 

One of the most versatile and common sampling devices 
in placer mining is the gold pan. It is used as a recon- 
naissance tool, a sampling tool, and a concentrate refining 
tool. With a gold pan, the prospector has the ability to, in 
effect, conduct his or her assay work on-site with immediate 
results. Although accuracy may be poor, the prospector can 
determine in the field if gold is present and in roughly what 
amounts. 

The gold pan uses gravity separation to concentrate 
heavy minerals. Pans come in a variety of sizes, ranging 
in diameter from 12 to 16 in. An experienced panner can 
concentrate approximately 0.5 yd 3 gravel daily. Because of 
this limited capacity, panning can be costly when large 
volumes must be processed; however, low capital expense, 
ease of use, versatility, and portability make the gold pan 
invaluable. 

Immediate feedback when exploring or mining is a 
prime advantage of the gold pan. This one feature is ex- 
tremely important for eliminating areas of low potential 
during exploration, and for separating pay gravel from 



Bucket drilling, although not as popular as churn drill- 
ing, has important applications in placer deposit evalua- 
tion. Under ideal conditions, this technique is relatively fast 
and provides large samples. In this system, a standard 
rotary drill is equipped with a special "bucket" bit con- 
sisting of a 30- to 48-in-diam cylinder, 3 to 4 ft long. The 
bit is driven down through the deposit, using the rotational 
force of the drill, until the cylinder is full. As the bit is 
withdrawn, a mechanism closes off the bottom of the bit 
retaining the sample. The process is then repeated until the 
desired depth is reached. 

Bucket drills perform best in sands, soils, pebbles, and 
clays. Progress is slow, and sometimes impossible, in ground 
containing boulders, cemented gravel layers, and bedrock. 
The size of the bit tends to disperse drilling force over a large 
area, thereby reducing the effective penetration rate. For 
this reason the bucket drill quickly becomes inefficient in 
hard or compact material. Problems are also encountered 
in saturated ground, where water often washes away a por- 
tion of the sample as the bit is withdrawn. 

Bucket drilling extracts a much larger sample than 
other drilling methods. Consequently, the influence of the 
bit on compaction and expansion of material is reduced. 



ROTARY DRILLING 

This type of drill, commonly used for drilling large- 
diameter blastholes in surface mining, has found limited 
use in placer exploration. The only way to obtain a sample 
with this machine is to analyze drill cuttings. Because the 
method does not provide a core, it is difficult to associate 
a volume with the recovered material, and it is hard to 
estimate the depth horizon of the sample. 

Rotary drills are useful in that they provide a fast, in- 
expensive way to determine the depth of bedrock. Holes pro- 
vided by rotary drills range from 6 to 15 in. in diameter 
and reach any depth required for placer mining. Virtually 
any material can be drilled, and penetration rates are far 
superior to any other placer drilling method. Regardless of 
the steps taken, however, it is difficult to accurately 
estimate deposit grade with samples obtained from rotary 
drilling. 



TRENCHING 

In fairly shallow, dry deposits, trenching with a backhoe 
is an extremely effective sampling technique. The procedure 
involves digging a trench to bedrock, then obtaining 
material from a channel taken down one side of the trench. 
This material is then measured and analyzed, providing a 
grade estimate. Another method relates an assay analysis 
of all the material extracted by the backhoe to the volume 



of the trench. The disadvantage of this method is the in- 
ability to determine the horizon of valuable mineral con- 
centration. With either method, large-volume samples are 
available at a low cost. 

In sampling situations, backhoes can excavate from 20 
to 45 LCY/h. Sample control is typically good with little 
volume distortion or material dilution under properly con- 
trolled circumstances. Backhoes are relatively inexpensive, 
easy to operate, versatile, and readily available. The 
machine can dig a variety of formations, and digging depths 
as much 30 ft below the machine platforms are possible. 
In saturated ground, keeping the trench open for sampling 
is normally a major problem. 



SEISMIC SURVEYS 

In placer mining, bedrock depth plays a key role. 
Although not always the case, gold tends to concentrate 
near, on, or even in bedrock in a majority of placer deposits. 
Consequently, it is imperative to understand the nature of 
the bedrock and to design a mining method and select equip- 
ment based on its depth. 

One method of determining bedrock depth is seismic 
refraction or reflection. In simple terms, the technique in- 
volves bouncing sound energy off the relatively resistant 
bedrock to determine its depth. The method is much cheaper 
than drilling a series of holes and, if bedrock proves to be 
too deep for practical mining, may prevent unnecessary 
drilling. 



MINING 



Next, a method for excavation and and transportation 
of material contained in the deposit is needed. Mining 
methods are typically dictated by several basic factors. 
Deposit depth, size, and topography are of primary impor- 
tance. The geologic nature of the deposit and accompany- 
ing overburden both play key roles. Types of equipment ob- 
tainable locally, sources of power, and the availability of 
water are all important factors. In some cases, operators 
may simply feel more confident using one method of extrac- 
tion as opposed to another, even if local conditions are 
unfavorable. 

In any event, the mining method should be designed 
with one fundamental goal in mind: To extract pay gravel 
from the deposit and move it to the mill at the lowest possi- 
ble overall cost. Several basic concepts should be designed 
into the mining method to keep costs low. These include 

1. Haul only pay gravel to the mill. Eliminate hauling 
and processing unprofitable material. 

2. Handle both overburden and pay gravel as few times 
as possible. Do not pile overburden or tails on ground that 
is scheduled for excavation. 

3. Locate the mill at a site that minimizes average pay 
gravel haul distance. In most instances, it is cheaper to 
pump water than to haul gravel. 

4. Do not mine gravel that is not profitable even if it con- 
tains gold. Money is lost for every yard of gravel mined if 
that gravel does not contain enough value to pay for the 
cost of mining and processing. 

As can be seen, common sense plays a large role in the 
proper design of a placer mine. The same holds true for mine 



equipment selection. Countless combinations of equipment 
have been tried in attempts to effectively mine placer 
deposits. Equipment typically used in the western United 
States includes 

1. Backhoes (hydraulic excavators). 

2. Bulldozers. 

3. Draglines. 

4. Dredges. 

5. Front-end loaders. 

6. Rear-dump trucks. 

7. Scrapers. 

Each type of equipment is suited to a particular task. 
In some instances, only one piece of equipment may be 
used to remove overburden, excavate and haul pay gravel, 
and place mill tailings and oversize (i.e., bulldozers). More 
often, several different types of equipment are utilized to 
take advantage of their specific attributes. 

When selecting placer mining equipment, the evaluator 
must consider two important concepts. First, the volume 
of earth in place is less than the volume of the same earth 
after excavation. This point is critical in cost estimation and 
must be remembered. Because placer gravel is relatively 
light, placer mining equipment is typically limited by 
volume capacity, not weight capacity. For this reason, mine 
equipment capacities and associated cost equations in this 
report are based on volume after accounting for material 
swell— in loose cubic yards. Resource estimates are typically 
stated in bank cubic yards— the volume before accounting 
for material swell. This has a significant meaning to the 
design of a placer mining system. To mine a 500,000-BCY 






deposit, equipment will have to move 570,000 LCY of gravel 
if the material swells 147c (typical for gravel deposits). 
Although the total weight of material moved is constant, 
equipment will have to move a larger volume of gravel than 
the in-place estimate indicates. As a result, the mining 
system should be designed around the total loose cubic yards 
of gravel to be moved, not the total bank cubic yards. 

Second, mine equipment equations in section 2 of this 
report are based on the maximum amount of overburden, 
pay gravel, and mill tails moved daily. Although average 
volume handled might be less, equipment must be selected 
to handle the maximum load. 

To aid in mine planning, and to obtain reasonable 
capital and operating mine costs, the following information 
will typically be required: 

1. Total length and average width of haul and access 
roads. 

2. Total surface area of deposit. 

3. Nature of ground cover. 

4. Topography of deposit area. 

5. Total loose cubic yards of overburden, and maximum 
amount of overburden handled daily. 

6. Total loose cubic yards of pay gravel, and maximum 
amount of pay gravel handled daily. 

7. Total cubic yards of mill tails handled daily. 

8. Type of equipment desired. 

9. Average haul distances and gradients for overburden, 
pay gravel, and tailings. 

The following is a discussion of the principal types of 
equipment used in excavating and hauling overburden, 
placer gravel, and mill oversize and tails, and may be used 
to aid in mine design and equipment selection. 



BACKHOES (HYDRAULIC EXCAVATORS) 

The backhoe is one of the most efficient types of equip- 
ment for bedrock cleanup. It is most often used for the ex- 
traction of pay gravel, but can also be used for excavation 
of overburden. The machine has almost no capacity for 
transportation of material and for that reason is used in 
conjunction with either front-end loaders, trucks, or in some 
cases, bulldozers. Depending on bucket selection, the 
machine can handle a variety of ground conditions including 
clays, poorly sorted gravels, tree roots, and vegetation. Dig- 
ging depths of over 30 ft are obtainable with certain 
backhoes, but production capability decreases rapidly as 
maximum digging depth is approached. 

Backhoes typically used in the western United States 
are capable of excavating from 95 to 475 LCY/h. Sizes range 
from 105-hp machines with 0.5-yd 3 buckets to 325-hp units 
with 3.75-yd 3 buckets. Capacity is contingent upon digging 
difficulty, operator ability, swing angle, digging depth, and 
obstructions. 

The backhoe is ideal for situations where bedrock 
cleanup is critical, obstructions exist in the mining area, 
and other means of transporting gravel are available. 



BULLDOZERS 

The bulldozer represents an extremely versatile tool in 
placer deposit extraction, and is the most popular. It can 
be used for overburden removal, pay gravel excavation, 



bedrock cleanup, overburden and pay gravel transportation, 
road construction, tailings placement, and a variety of 
minor functions. The bulldozer is the only device capable 
of handling all tasks required for placer mining in a prac- 
tical manner and must be considered if capital is scarce. 

Although bulldozers can handle all placer mining func- 
tions, they are not necessarily the most efficient machine 
for any one task. With its ripping capacity, the bulldozer 
is capable of cleaning up bedrock; however, the backhoe is 
much more selective and efficient. The bulldozer can, and 
often is, used to transport gravel, but in most cases trucks, 
scrapers, and front-end loaders can each do the job cheaper 
if haul distances are more than a few hundred feet. In ad- 
dition, bulldozers are not well suited to more large volumes 
of gravel or to dig to excessive depths. In both instances, 
draglines exhibit superior performance. 

A major advantage of the bulldozer is its ability to ex- 
cavate, transport, and load the mill all in one cycle, 
eliminating the need for expensive rehandling. Dozer 
capacities for excavating and hauling range from 19 LCY/h 
for a 65-hp machine up to 497.5 LCY/h for a 700-hp dozer 
(based on a 300-ft haul distance). Capacity is dependent 
upon ripping requirements, operator ability, cutting 
distance, haul distance, digging difficulty, and haul 
gradient. 

Dozers are best suited for situations where deposit and 
overburden thicknesses are not excessive, few large obstruc- 
tions are present, and haul distances average less than 
500 ft. 



DRAGLINES 

Draglines are well suited for excavating large quantities 
of overburden, gravel, and waste. Although their material 
transporting ability is limited, draglines with booms up to 
70 ft long are capable of acting as the sole piece of mining 
equipment. As with the bulldozer, draglines can excavate 
overburden and pay gravel, load the mill, and remove tail- 
ings; however, draglines are relatively inefficient at bedrock 
cleanup, and do not handle difficult digging as well as 
backhoes or dozers. 

Depths of over 200 ft are obtainable with this type of 
machine, and when used in conjunction with front-end 
loaders or rear-dump trucks, large-capacity operations are 
possible. Draglines handle from 28 LCY/h for a 84-hp unit 
to 264 LCY/h for a 540-hp machine. Capacity is dependent 
upon bucket efficiency, swing angle, and operator ability. 

Draglines are ideal for overburden removal and for 
large, deep deposits where bedrock cleanup is not critical. 
They must, however, be matched with the right equipment 
(i.e., portable mills or gravel transportation machinery). 



DREDGES 

Cost estimation equations for dredging are not in- 
cluded in this report. Dredges, except for recreational units 
and small machines used in active channels, are designed 
for high-capacity excavation of specific placer environments. 
The machines are best utilized in large volume, relatively 
flat-lying deposits that occur below water level. Because of 
large capital investment requirements and a scarcity of 
ground suitable for large-scale dredging, they are uncom- 
mon in the western United States. 



Operating costs for large-capacity dredges average ap- 
proximately $0.70/yd 3 . Purchase and refurbishing costs are 
often more than $3 million, and can run over $10 million. 
In large-volume situations, dredges must be considered. 
Because suitable applications are rare, however, they have 
not been included in this report. 



FRONT-END LOADERS 

This versatile machine is capable of many functions. In 
the western United States, its primary use is hauling 
previously excavated gravels, and the subsequent loading 
of the mill. Although front-end loaders are not the most ef- 
ficient hauling unit, their self-loading ability provides many 
advantages. One is the elimination of the need to match 
the excavation machine with the haul unit. With a front- 
end loader, the excavator can operate at its own pace and 
simply stockpile material. The loader then feeds from the 
stockpile and transports gravel to the mill feed hopper. This 
removes the problem of matching excavator output with 
truck cycles or mill feed rates. 

The machine is also capable of removing and transport- 
ing mill oversize and tailings; however, front-end loaders 
are not particularly adept at excavating consolidated 
material. If overburden or gravel are at all compacted, a 
backhoe or bulldozer should be used for a primary 
excavation. 

Front-end loaders are capable of hauling from 24 LC Y/h 
for a 65-hp, 1-yd 3 machine to 348 LCY/h for a 690-hp, 12-yd 3 
machine (based on a 500-ft haul distance). Capacity varies 
with haul length, haul gradient, operator ability, bucket 
efficiency, and type of loader. 

Front-end loaders are best utilized as haul units over 
distances of less than 1,000 ft. Their versatility makes them 
useful for pay gravel and overburden transportation, mill 
oversize and tailings removal, and general site cleanup. 



REAR-DUMP TRUCKS 

Trucks represent the least expensive method of material 
movement over long distances; however, since other 
machinery is required for loading, total gravel transporta- 
tion expenses over short distances may be higher than for 
front-end loaders or scrapers. Trucks generally serve two 



purposes: Material movement and mill feed. They have 
relatively low capital costs and require little maintenance 
compared to other placer equipment. Trucks do need fairly 
good road surfaces and require careful matching with 
loading equipment to achieve acceptable efficiency. 

Capacities for units at small placer operations range 
from 3 to 47.5 yd 3 . Trucks are most productive over haul 
distances of 1,000 to 10,000 ft and can travel faster than 
equivalent-sized scrapers or front-end loaders. Production 
capacities range from 32.3 LCY/h for a 3-yd 3 truck to 444.8 
LCY/h for a 47.5-yd 3 truck (based on a 2,500-ft haul 
distance). Capacity is contingent upon loader capacity, haul 
distance, and haul gradient. 

Trucks are suited to operations where a fixed mill is 
situated more than 0.5 mile from the minesite. They are 
equally effective hauling pay gravel, overburden, or mill 
tailings and oversize, but must be accompanied by a method 
of material loading. 



SCRAPERS 

These machines are noted for their high productivity 
when used to transport overburden, pay gravel, and tail- 
ings. As with front-end loaders, scrapers are self-loading, 
although bulldozers or other scrapers often assist. They are 
capable of much higher speeds and greater capacity than 
front-end loaders, and exhibit haulage characteristics 
similar to rear-dump trucks. Scrapers, however, are more 
costly to purchase and maintain. 

Scrapers are limited in their ability to excavate con- 
solidated or unsorted material. A bulldozer equipped with 
a ripper must precede them in overburden or gravel that 
is not easily drifted. If boulders are present, they must either 
be blasted or removed by other means. The nature of the 
scraper-dumping mechanism renders them unsuitable for 
direct mill feed. When used to haul pay gravel, scrapers will 
typically unload near the mill, and bulldozers will then be 
used to feed material. 

Capacities range from 201 LCY/h for a 330-hp machine 
to 420 LCY/h for a 550-hp machine (based on a 1,000-ft haul 
distance). Capacity is contingent upon haul distance and 
gradient, and loading procedure. 

In placer mining, scrapers are best utilized for transpor- 
tation of unconsolidated overburden or mill tailings over 
distances ranging from 500 to 5,000 ft. 



PROCESSING 



Often the most difficult part of placer mining is achiev- 
ing the desired recovery of valuable minerals from mine- 
run gravel. The design of a successful mill is a specialized 
science and often proves difficult even for those actively in- 
volved in placer mining. Great care must be taken to en- 
sure the recovery of a high percentage of contained valuable 
minerals. Obviously, the profitability of an operation is 
directly related to the percentage of contained valuable 
minerals recovered by the mill. 

Although mill design can be difficult, the basic premise 
used in heavy mineral recovery is quite logical. In placer 
deposits, high-density minerals have been concentrated by 



combinations of natural phenomenon such as gravity, tur- 
bulent fluid flow, and differences in mineral density. Con- 
sequently, it would seem practical to utilize these conditions 
to further concentrate heavy minerals. This form of mineral 
recovery is referred to as gravity separation and is the basis 
for most placer mills. 

Gravity processes must consider both particle specific 
gravity and size for effective separation. Differences in 
specific gravity alone will not distinguish various materials. 
It is the differences in weights in a common medium that 
creates efficient separation. Consequently, a particle of high 
specific gravity and small size may react the same as a large 



particle with low specific gravity in a given fluid. If grav- 
ity separation is to be effective, size control must be im- 
plemented to take advantage of differences in particle 
specific gravity. 

Equipment used for gravity separation ranges from gold 
pans to prebuilt self-contained placer plants. In general, the 
most widely employed devices in the western United States 
are 

1. Jig concentrators. 

2. Sluices. 

3. Spiral concentrators. 

4. Table concentrators. 

5. Trommels. 

6. Vibrating screens. 

Of these devices, trommels and vibrating screens are 
used for particle size classification, and the remainder are 
forms of gravity concentrators. In addition, feed hoppers and 
conveyors are needed for surge capacity and material 
transportation. These items, which are commonly neglected 
in plant costing, must be carefully selected to ensure prop- 
er plant operation. 

Although the complete design of a placer recovery plant 
cannot be thoroughly covered in the space available here, 
three sample flowsheets illustrating basic placer mill design 
are included at the end of this section on processing. Along 
with a flow sheet detailing equipment type, size, and capa- 
city required for the mill, the following will be needed to 
obtain an accurate cost estimate using this report: 

1. Maximum feed capacity of the mill. 

2. A material balance illustrating feed, concentrate, and 
tailings rates. 

3. The purpose of each gravity separation device (rougher, 
cleaner, scavenger, etc.). 

4. Method of removal and transportation of mill tails and 
oversize. 

The following discussion details equipment used in 
gravity separation and may prove useful in mill design. 



CONVEYORS 

As material travels through a mill circuit, it can be 
moved by conveyor, pumped in a slurry, or transferred by 
gravity. In placer processing mills, material is most often 
transported in a slurry or by gravity. In some cases, 
however, conveyors are necessary. Conveyors are typically 
used for situations of extended transport where material 
need not be kept in a slurry, such as the removal of over- 
size or tailings. They provide an inexpensive method of 
transporting large quantities of material over fixed 
distances. In the case of placer processing plants, this 
distance typically ranges between 10 and 120 ft. Conveyors 
used in these plants are typically portable, and consequently 
come complete with framework and support system ready 
to operate. 

Conveyor capacity is related to belt width, belt speed, 
and material density. For most placer gravels, capacities 
range between 96 yd 3 /h for an 18-in-wide belt to 480 yd 3 /h 
for a 36-in-wide belt. 



FEED HOPPERS 

The initial piece of equipment in most mill circuits is 
a feed hopper. The hopper is used in conjunction with a 



feeder to smooth out material flow surges introduced by 
loading devices with fixed bucket sizes (front-end loaders, 
rear-dump trucks, etc.). Hoppers often contain a grizzly in 
order to reject large oversize material. The feeder, typically 
a vibrating tray located under the hopper, transfers gravel 
at an even rate to the circuit. Although the hopper-feeder 
combination may appear to be a minor piece of equipment, 
a steady flow of material through the mill is very impor- 
tant for effective gravity separation. 

Hopper capacity and feeder capacity are two separate 
items. Generally, hoppers are designed to hold enough 
material to provide a steady flow of gravel despite surges 
inherent in mining cycles. Feeders are set to provide the 
appropriate flow rate to the mill. So even though a hopper 
may have a 100-yd 3 capacity, the feeder might provide 
material at 20 ydVh. 

Feeders are not always used in placer mills. When they 
are not used, feed rate is regulated by the size of the open- 
ing in the bottom of the hopper. The cost estimation curves 
in this report calculate hopper-feeder costs based on feeder 
capacity, which typically equals mill capacity. Factors are 
provided for situations where feeders are not used. 



JIG CONCENTRATORS 

Jigs are gravity separation devices that use hindered 
settling to extract heavy minerals from feed material. They 
typically consist of shallow, perforated trays through which 
water pulsates in a vertical motion. In most instances, a 
bed made up of sized shot, steel punchings, or other 
"ragging" material is placed over the perforations to pro- 
mote directional currents required for separation. Slurried 
feed flowing over the bed is subjected to the vertical pulsa- 
tions of water, which tend to keep lighter particles in 
suspension while drawing down heavier constituents. These 
heavy minerals are either drawn through the bed and 
discharged from spigots under the jig or, if too large to pass 
through the perforations, are drawn off near the end of the 
machine. Lighter particles continue across and over the end 
of the jig as tailings. 

Jigs are sensitive to feed sizing. They are generally 
utilized for feeds ranging from 75 ^m to a maximum of 1 
in, but recoveries improve if feed is well sized and kept to 
minus 0.25 in. Efficiency is maximized when feed materials 
have been deslimed and sized into a number of separate frac- 
tions for individual treatment. Optimum solids content for 
jig plant feed ranges from 35% to 50%— the object being to 
avoid excessive dilation of the material. Capacities for jigs 
range from 0.1 to 400 yd 3 /h and are dependent upon desired 
product as well as equipment size. 



SLUICES 

The most common gravity separation device used in 
placer mills, sluices are simple to construct, yet effective 
heavy mineral recovery tools. Sluice design is quite diverse 
and opinions differ widely with respect to capacity, riffle 
design, and recovery. In general, capacities and perfor- 
mances vary with box width and slope, gold particle size, 
nature of feed, and availability of water. 

Sluices are primarily used for rough concentration and 
are capable of processing poorly sorted feeds. As with other 
methods, however, recovery is related to the degree of 
previous sizing. 






Sluice design can be quite complex but usually is a mat- 
ter of trial and error. Several basic principles typically 
apply. Width is determined by the maximum and minimum 
volume of water available, the size and quantity of over- 
size feed that must be transported, and the slope. Length 
depends principally on the character of the gold. Coarse gold 
and granular gold settle quickly and are easily held in the 
riffles, while fine gold and porous gold may be carried some 
distance by the current. Velocity of the water is controlled 
primarily by the slope. In general, the sluice should be con- 
structed and installed so that water flowing through the 
box will transport oversized material and prevent sand from 
packing the riffles. 

If the surface of the water flowing through the sluice 
is smooth, the bottom of the sluice is probably packed with 
sand, allowing little gold to be saved. The desired condi- 
tion occurs when waves form on the surface of the water 
flowing through the sluice, and these waves, along with the 
wave-forming ridges of material on the bottom of the sluice, 
migrate upstream. This indicates an eddying or boiling ac- 
tivity on the lee side of the ridges, which maximizes gold 
recovery and tailings transport. Consequently, the sluice 
attains maximum efficiency when riffle overloading is 
incipient. 

Sluices are generally considered to be high-capacity 
units, with a 12-in-wide sluice box capable of handling 15 
yd 3 /h if sufficient water is available. A 24-in-wide sluice can 
handle up to 40 yd 3 /h, and 48-in-wide sluices have reportedly 
processed up to 200 yd 3 /h. Of course, a sluice will handle 
as much gravel as the operator wants to push through it. 
However, to ensure reasonable recovery, capacity is limited 
by box width and slope, water availability, and feed 
characteristics. 

Feed slurry densities are highly variable and range from 
1% to 35% solids by weight, averaging 10%. Water use can 
be reduced significantly if the larger of the oversize is 
eliminated from the feed. Sluices require no power to 
operate unless a pump is needed to transport water or 
slurry. One disadvantage of the sluice is the necessity to 
halt operations in order to recover concentrates. 



SPIRAL CONCENTRATORS 

Spirals are used infrequently in the western United 
States but may be applicable for certain types of feed. These 
gravity separation devices exhibit several desirable 
features. They accept sized slurry directly, and require no 
energy to operate other than perhaps pumps for material 
feed. Pumps can be excluded if gravity feed is used. Selec- 
tivity is high because of adjustable splitters within the 
slurry flow. Spirals can be used to produce a bulk concen- 
trate, scavenge valuable minerals from tailings, or in some 
instances, recover a finished concentrate. The ability to pro- 
duce a finished concentrate will be limited to feeds that con- 
tain a higher concentration of desired product than typically 
found in most gold placer feeds. 

To save space, two or three spiral starts are constructed 
around a common vertical pipe. This arrangement takes lit- 
tle floor space, allowing banks of multiple units to be set 
up for large-capacity requirements. In this situation, slurry 
distributors are required to sectionalize feed for individual 
spirals. 

Maximum feed rates vary according to feed particle den- 
sity, size, and shape. Rates generally range from 1.0 to 1.4 



yd 3 /h roughing down to 0.3 to 0.5 yd 3 /h cleaning per start. 
Feed slurry density is typically less than 25% solids by 
weight, necessitating the use of larger pumps than needed 
for jigs or tables. 



TABLE CONCENTRATORS 

Concentrating tables (shaking tables) are one of the 
oldest methods of mechanical gravity concentration. 
Although capable of handling a variety of feed types and 
sizes, their optimum use is wet gravity cleaning of fine con- 
centrates ranging from 15 jum to 1/8 in. The unit consists 
of a large, flat, smooth table, slightly tilted, with riffles at- 
tached to the surface. A longitudinal reciprocating motion 
is introduced to the deck by means of a vibrating mechanism 
or an eccentric head action. 

Although limited in capacity, tables have the advantage 
of being easily adjustable by regulating the quantity of wash 
water and altering the tilt angle of the deck. The results 
of these changes are immediately observable on the table. 
With the addition of splitters, efficient control of high-grade 
concentrate recovery, middling recovery, and tailings pro- 
duction is possible. 

Solids content for table feeds averages approximately 
25% by weight. Stroke length and speed are adjusted ac- 
cording to feed. Long strokes at slow speeds are used for 
coarse feeds; fine material responds better to short strokes 
at higher speeds. A reciprocating speed of 280 to 380 
strokes/min will handle most feeds. Table capacities range 
from 0.05 to 8 yd 3 /h and depend on desired product as well 
as equipment size. 



TROMMELS 

This machine is the most common size classification 
device used in gold placer mills and is well suited for this 
task if properly designed. Trommels consist of a long 
rotating cylinder that is typically divided into two sections. 

In the first section, lengths of angle iron or similar 
material are fastened to the inside of the rotating drum. 
These act as lifters to carry feed up the side of the rotating 
cylinder. As material reaches the top of the rotation, it falls 
back to the bottom of the cylinder and breaks upon impact. 
This action, along with water introduced under pressure, 
serves to break up compacted soils and clays, and liberate 
valuable minerals. 

The second section consists of perforations in the 
cylinder walls positioned along the length of the drum. 
Typically, perforation size will graduate from 1/8 in, to 3/16 
in, to 1/4 in as the feed progresses down the trommel. 

Sized fractions are drawn directly below the section of 
the trommel in which they are separated. They generally 
flow to either a vibrating screen to be sized further or to 
a gravity separation device. Oversize material is discharged 
out the end of the trommel as waste. 

Trommels are particularly well adapted to placer feeds 
because of their ability to handle a diversity of feed sizes 
and to break up material in the scrubber section. Capacity 
ranges from 10 to 500 yd 3 /h and is dependent on feed 
characteristics, screen perforation sizes, and machine size. 
Water requirements are contingent upon the amount of 
washing desired. 



10 



VIBRATING SCREENS 

Vibrating screens are often used for secondary size 
classification in circuits treating alluvial ores and, in some 
cast's, may provide primary sizing. The machines consist 
of a deck, or decks, containing inclined screening surfaces 
that are vibrated in either a rectilinear or elliptical motion. 
Screening medium can be woven wire cloth, parallel bars, 
or punched sheet metal. 

High capacity, ease of installation, and reasonable 
operating costs have all contributed to the popularity of 
vibrating screens. The practical minimum size limitation 
for production screens is about 100 mesh, although 
325-mesh separations have been achieved. Capacity is, of 
course, dependent on many factors. These include type of 
material, amount of oversize, amount of undersize, moisture 
content, particle shape, screen opening size, and screen 
medium. In general, from 0.40 to 0.75 ft 2 of screen surface 
area will be needed for every cubic yard of feed handled per 
hour. 

SAMPLE MILL DESIGN 

It is not possible to provide complete instruction on mill 
design within the constraints of this manual. Mills must 
be planned with the intention of treating the size, shape, 
and grade characteristics of a specific feed. Sample gold mill 
flowsheets shown in figures 1, 2, and 3 are included to aid 
the evaluator in cost estimation only. They are provided 
to demonstrate that, in most instances, material will have 
to be fed, washed, sized, and separated for proper recovery. 

Tables 1, 2, and 3 provide sample material balances for 
these mills. 



Table 1. — Sample material balance, sluice mill 

(Specific gravity: Gold, 17.50; waste, 2.81) 



Feed 



Concentrate 



Feed 



Concentrate 



Tails 



Rate yd 3 /d. . 120 0.1 119.9 

Composition wt%.. 100 0.08 99.92 

Specific gravity 2.81 2.82 2.81 

Grade trozAu/yd 3 .. 0.040 42.24 0.005 

Gold distribution: 

tr oz/d 4.8 4.224 0.576 

°/o 100 88 12 



Table 2.— Sample material balance, jig mill 

(Specific gravity: Gold, 17.50; waste, 2.65) 



Tails 



Rate yd 3 /d.. 700 0.1 699.9 

Composition wt %. . 100 0.01 99.99 

Specific gravity 2.65 2.71 2.65 

Grade trozAu/yd 3 .. 0.030 199.50 0.002 

Gold distribution: 

tr oz/d 21.0 19.95 1.05 

% 100 95 5 



Table 3.— Sample material balance, table mill 

(Specific gravity: Gold, 17.50; waste, 2.73) 



Rate yd 3 /d . 

Composition wt % . 

Specific gravity 

Grade tr oz Au/yd 3 . 

Gold distribution: 
tr oz/d 



Feed 


Concentrate 


Tails 


250 

100 

2.73 

0.045 


0.2 

0.08 

2.75 

53.44 


249.8 

99.92 

2.73 

0.002 


11.25 
100 


10.688 
95 


0.562 
5 



10-st capacity 
rear-dump truck 



Oversize 4- 



Plus 0.5 in 
(7.5 yd 3 /h) 



Conveyor 



Dump 



Tails 

(4.49 yd 3 /h) 



Mine-run gravel 
(12 yd 3 /h) 

I 



Feed hopper 



Feed belt 



Trommel 



Minus 0.5 in 
(4.5 yd 3 /h) 



Sluice 



Concentrates 
(0.01 yd 3 /h) 



Panning 



Gold product 



(200 gpm) 



-> Water 



Settling pond 



Pump 



Recycled water 



Figure 1.— Sample flow sheet, sluice mill. 



Dragline 



11 



Plus 4 in 
(5 yd 3 /h) 



Plus 1.5 in 
(20 yd 3 /h) ' 



Waste 
(28 yd 3 /h) 



Scavenger 
sluice 



Gold product 



Waste 
(1.5 yd 3 /h) 



Black sand 
(0.49 yd 3 /h) 



Mine-run gravel 
(70 yd 3 /h) 



Grizzly 



(800 gpm) 



Minus 4 in 



Vibrating 
screen 



Minus 0.5 in 
(30 yd 3 /h) 



Jig sump 



Jig pump 



Dewatering 
bin 



Cleaner 
jig 



Gold and black sands 
(0.5 yd 3 /h) 

I 



Final jig 



Concentrate 
(0.01 yd 3 /h) 

I 



Panning 



Gold product 



Minus 1.5 to plus 0.5 in 
(15 yd 3 /h) 



Sluice 



Waste 
(15 yd 3 /h)' 



Plus 0.5-in 











nuggets 




— fe 




Sluice 




Minus 0.5-in 






nuggets 


h 














-^ 


Rougher 

jig 




Jig tray 




^ 






w 


Min 


I 

js 0.125-in concen 

(2 yd 3 /h) 

I 


Plus 0.125-in nuggets 
trate 



Gold product 



-► Water 



Settling pond 



Pump 



Recycled water 



Dump 



Figure 2.— Sample flow sheet, jig mi 



12 



Bulldozer 



Mine-run gravel 
(25 yd 3 /h) 



Oversize 
(8.25 yd 3 /h) 



Conveyor 



r 



Minus 0.25 in 
(5.25 yd 3 /h) 



Feed hopper 



Feed belt 



Trommel 



Minus 0.125 in 
(5 yd 3 /h) 



(500 gpm) 



+\ 



Minus 0.0625 in 
(6.5 yd 3 /h) 



Waste 
"(0.49 yd 3 /h) 



Conveyor 



Waste 
(0.49 yd 3 h) 



Coarse sluice 



Concentrate 
(0.1 yd 3 /h) 



Coarse table 



4_^\ 



Middling sluice 



r\ * 



Concentrate 
(0.2 yd 3 /h) 



Middling table 



— >«- 



Concentrates 
(0.01 yd 3 /h) 



y\ 



Panning 



Fines sluice 



Fines table 



Oversize 
(14.75 yd 3 /h)~ 



Concentrates 
' (0.01 yd 3 /h) 



r\ \ + ». Tails 

(15.25 yd 3 /h) 

Concentrate 
(0.2 yd 3 /h) 



Vibrating 
screen 



Minus 0.125 in 
(0.5 yd 3 /h) 

I 



Fines sluice 



Gold product 



I 

Waste 

(0.49 yd 3 /h) 

I 



Settling pond 



Pump 



Dump 



Recycled water- 



Figure 3.— Sample flow sheet, table mill. 



13 



SUPPLEMENTAL SYSTEMS 



Commonly neglected in costing and design work, sup- 
plemental systems gain importance in placer operations. 
Because of the relative low cost of placer mining and mill- 
ing equipment and systems, the expenses associated with 
supplemental items represent a larger percentage of the 
total cost than with other types of mining. For costing pur- 
poses, any system, structure, or equipment not directly 
related to production but necessary for continued operation 
is categorized as supplemental. These include 

1. Buildings. 

2. Camp facilities. 

3. General services and lost time. 

4. Generators. 

5. Pumps. 

6. Settling ponds. 

Each item included in the supplemental section should 
be examined to determine if it is needed at a particular 
operation. To aid in this determination and to assist in cost 
estimation of supplemental items, the following informa- 
tion will prove helpful: 

1. Location and elevation of available water in reference 
to the millsite. 

2. Ecological sensitivity of the area. 

3. An estimate of the number and capacity of pumps 
needed. 

4. Maximum hourly capacity of mill. 

5. Building requirements. 

6. An estimate of workforce size. 



BUILDINGS 

Many placer operators consider any building to be a lux- 
ury; however, if weather is a factor or if operators desire 
to safely store equipment, some buildings will be needed. 
Typically, a small placer mine will have one structure that 
serves as a shop, a concentrate cleanup area, and a storage 
room. More elaborate operations, or those in areas of bad 
weather, will cover the mill and often construct several 
small storage sheds. These buildings are usually temporary 
structures of minimal dimensions constructed of wood or 
metal. 

The size of each building must be estimated for costing 
purposes. For the typical operation, the main structure will 
be capable of housing the largest piece of mobile equipment 
at the mine with enough additional room for maintenance 
work. Shops often have concrete floors, and power and water 
facilities are typically provided. Storage sheds are usually 
of minimum quality, have a wood floor if any at all, and 
often contain power for lighting. Factors for all these 
variables are provided in the building cost estimation curve. 



by the workers in their trailers with an allowance provided 
for the cost of food. 

To calculate the expense of camp facilities, it is 
necessary to estimate the number of people staying at the 
mine. Guidelines for this estimate are provided with the 
cost equations in section 2 of this report. It must be 
remembered that the number of people working at any one 
operation can be quite variable, and if the number of in- 
tended or actual employees is available, this figure must 
be used. 



GENERAL SERVICES AND LOST TIME 

Compared with other methods of mineral recovery, 
placer mining is relatively inefficient. Because of limits in 
workforce size, delays and tasks not directly related to min- 
ing have a noticeable effect on productivity. This 
inefficiency strongly influences costs associated with placer 
mining, and must be taken into account. 

In placer mining, most costs associated with inefficiency 
can be attributed to three distinct areas: 

1. Equipment downtime. 

2. Site maintenance. 

3. Concentrate refinement. 

Specific expenses can be further delineated. 

1. Equipment downtime. 

A. Productivity lost by the entire crew because of 
breakdown of key pieces of equipment. 

B. Productivity lost by individual operators because 
of breakdown of single pieces of equipment. 

C. Labor charges of outside maintenance personnel. 

2. Site maintenance. 

A. Road maintenance. 

B. Stream diversion. 

C. Drainage ditch construction and maintenance. 

D. Site cleanup. 

E. Reclamation grading and recontouring. 

F. Settling pond maintenance. 

G. Mill relocation. 

3. Concentrate refinement. 

A. Concentrate panning. 

B. Mechanical separation. 

C. Amalgamation. 

Estimates indicate that in placer mining up to 37% of 
the total labor effort is spent on the above tasks. The lost 
time and general services cost curve must be used in all 
placer mine cost estimates. 



GENERATORS 



CAMP FACILITIES 

The provision of facilities for workers is an important 
part of placer operations. In most situations, workers will 
stay at the site during the mining season to take advan- 
tage of good weather. The needs of these workers must be 
met, and that typically involves providing living quarters 
and food. In almost all cases, employee housing at placer 
mines consists of mobile homes or trailers with a minimum 
amount of support equipment. Cooking is generally done 



In all but the most simple gravity separation mills, 
power will be needed to operate equipment. A minor amount 
of power will also be required for camp functions. Typically, 
power is provided by one of three sources: 

1. Individual diesel engines driving each piece of 
equipment. 

2. Diesel generators. 

3. Electrical power brought in through transmission 
lines. 

The third source generally requires excessive initial 
capital expenditures. Transmission lines are considered only 



14 



when the mill capacity is well over 200 ydVh, existing 
transmission lines are located near the site, or the mine 
life is expected to be 15 yr or more. Power source selection 
should be based on lowest overall cost and minimum en- 
vironmental impact. For most small- to medium-sized 
gravity separation mills in remote locations, diesel 
generators are selected to provide power. 

Cost estimation curves in this report are based on diesel 
generators providing all power to mill equipment. Electric 
power costs contained in individual processing equipment 
operating cost curves account for diesel generator operating 
costs. 



PUMPS 

Water, used to wash gravel and to initiate slurrying of 
the feed, is typically introduced as gravel enters the trom- 
mel or screen. More water is added as needed throughout 
the circuit to dilute the slurry or assist in washing. To pro- 
vide adequate washing, this water must be introduced 
under pressure which, in many cases, necessitates the use 
of pumps. Pumps will also be needed if mill water is to be 
recycled through settling ponds. Under certain cir- 
cumstances, one pump can handle all tasks required in a 
placer processing plant utilizing recycled water. It is 
preferable to minimize the use of pumps by taking advan- 
tage of gravity. 

Water use is dependent on several factors, including 

1. Washing required to properly slurry feed. 

2. Type of separation equipment used. 

3. Availability of water. 

4. Size and nature of valuable mineral constituents. 
For costing purposes, the evaluator must estimate the 

volume of water pumped per minute and the pumping head. 



A separate estimate must be made for each pump. Water 
requirements can either be calculated using parameters 
given in the processing portion of section 1, or roughly 
estimated using the following equation: 

Water consumption (gpm) = 94.089(X) 0546 , 

where X = maximum cubic yards of mill feed handled per 
hour. 

This equation provides the total gallons of water per 
minute consumed by the mill. Although not technically ac- 
curate, for the purposes of this report, head may be 
estimated as the elevation difference between the pipe 
outlet at the mill or upper settling pond, and the pump 
intake. 



SETTLING PONDS 

With the current level of environmental awareness, it 
is almost assured that mill water will have to be treated 
prior to discharge. Placer mines typically recycle mill ef- 
fluent through one or more settling ponds to control en- 
vironmental impact. 

To calculate the cost of settling pond construction using 
this report, only the maximum mill feed rate is required. 
Cost curves provide the construction expense of unlined 
ponds sized to comply with most regulations. In some in- 
stances, the pond will have to be lined with an impervious 
material. This is often required in ecologically sensitive 
areas, or in situations where underlying soils do not 
properly filter mill effluent, thereby increasing the turbidity 
of nearby streams. A factor is provided in the settling pond 
cost curve for impervious linings. 






ENVIRONMENT 



Enviromental costs are often decisive in placer mine 
economic feasibility. Costs associated with water quality 
control and aesthetics are inescapable and can represent 
a significant percentage of total mining expenses. Methods 
to minimize ecological disturbance are now considered an 
integral function of the mining sequence and are treated 
as such in cost estimation. 

Stream siltation from mill effluent and land disturbance 
from excavation are the main environmental problems fac- 
ing placer miners. Reduction of water quality is often the 
biggest problem, and many techniques have been devised 
to lessen the impact caused by mill operation. One method 
involves limiting mill operation to short periods of time, 
thus allowing effluent to disperse before additional mill 
discharge is introduced. Often the mill is designed with the 
intent of using as little water as possible for valuable 
mineral separation. The most common solution is mill water 
recirculation facilitated by the construction of settling 
ponds. These ponds are used to hold mill effluent until par- 
ticulate matter has settled; water from the ponds is then 
reused in the mill circuit. 

Mining of alluvial deposits necessitates disturbance of 
large areas of land. Typically all trees, brush, grasses, and 
ground cover will be cleared. This task alone may present 



a major stumbling block, because some States restrict open 
burning. Next, a layer of overburden is removed to expose 
the deposit. Finally, the valuable mineral-bearing gravel 
can be excavated. 

Current technology suggests that control of land dis- 
turbance be incorporated into the mining sequence. Mill 
tailings and oversize are typically dumped back into 
worked-out areas. Soil cover and overburden are removed 
just prior to pay gravel excavation, then hauled to mined- 
out areas to be graded and contoured over replaced tails. 
Often the surface is revegetated. In most instances, the 
operator will have no choice but to implement ecological 
control and reclamation procedures. Operators are typically 
required to post a bond to cover the cost of reclaiming mined 
lands, and if the surface is left disturbed, these bonds will 
be forfeited. 

Regulations vary from State to State, and may appear 
difficult and confusing at first; however, by contacting in- 
formation services at State capitals, operators will be 
directed to the agencies concerned. These agencies will 
detail regulations concerning placer operation and will also 
point out which Federal agencies might be involved (U.S. 
Forest Service or U.S. Bureau of Land Management). In 
most instances, contact will have to be made with both State 



15 



and Federal agencies. Typically, meeting environmental re- 
quirements for the State will satisfy Federal regulations. 
As stated earlier, environmental control is an integral 
part of mine and mill design, and costs are treated accord- 
ingly. Equations are provided for calculating the cost of mill 
tails and oversize placement. Expenses associated with 
grading and contouring are contained in the lost time and 



general services curve. An equation is also provided for the 
construction of settling ponds, if water is to be recycled. 
Bond costs are not included since requirements are 
highly variable. One other cost may arise that is not covered 
in section 2. This is the expense of replanting, and usually 
ranges from $100 to $200 per acre. 



COST ESTIMATION 



After selecting exploration, mining, milling, and sup- 
plemental techniques, the next step in cost estimation is 
the choice of appropriate cost curves. If the evaluator has 
completed the mine design prior to attempting cost estima- 
tion, this task consists of simply going through section 2 
of this report and selecting the proper equations. The list 
of capital and operating categories at the beginning of sec- 
tion 2 will aid in choosing individual curves. 

Costs used in deriving the estimation equations were 
collected from several sources. These include 

1. Placer mine operators. 

2. Mine equipment suppliers. 

3. Published cost information services. 

In all cases, cost figures quoted in the text and points 
used in cost equation derivations are averages of all data 
available. A bibliography of cost information publications 
follows section 2. Many of these sources contain both cost 
and capacity information and can be used to supplement 
this manual. 

Cost estimation methodology in this handbook is based 
on the Bureau's Cost Estimation System (CES), first 
published in 1977 as "Capital and Operating Cost Estima- 
tion System Handbook," by STRAAM Engineers, Inc. Pro- 
cedures for cost estimation using this report closely follow 
that publication. The cost estimation portion of this report 
is divided into operating and capital costs. Cost equations 
are similar for both with the only difference appearing in 
the units of the final answer. Capital costs are given in total 
dollars expended and operating costs in dollars per year. 

Using the appropriate curves, a separate cost is 
calculated for each capital and operating cost item. Only 
costs directly associated with the operation under evalua- 
tion need be calculated. All other cost items should be ig- 
nored. After calculation, item costs should be entered on 
the respective capital and operating cost summary forms 
(see figures 5 and 6 in section 2). 

Upon summation of individual expenses, a contingency 
may be added to both capital and operating costs. It is dif- 
ficult to anticipate every condition that may arise at a par- 
ticular operation, and the purpose of the contingency is to 
account for unforeseen expenditures. This figure is typically 
based on the degree of certainty of the evaluation in rela- 
tion to available information, and ranges from 10% to 20%. 

Cost per cubic yard of pay gravel processed is deter- 
mined by dividing the sum of all annual operating costs by 
the total amount of pay gravel processed per year. Summa- 
tion of individual capital expenditures produces the total 
capital cost. 

Use of the individual curves is described in the follow- 
ing paragraphs. 



COST EQUATIONS 

Capital and operating costs are divided into labor, equip- 
ment, and supply categories. One, two, or all three of these 
categories will be present in each cost equation. The sum 
of costs from each of these categories provides the total cost 
for any single cost item. To facilitate cost adjustments 
respective to specific dates, the labor, equipment, and supply 
classifications are further broken down into subcategories. 

Typically, each cost item will have a number of site ad- 
justment factors. These are provided to account for 
characteristics specific to a particular deposit. These fac- 
tors determine the precision of the final cost, so they must 
be selected and used carefully. Assistance in determining 
the correct use of a factor, or in understanding the 
parameters involved in a cost item, may be found in the 
preceding pages. 

To further improve cost estimates, labor rates are also 
adjustable. Rates can vary greatly for small placer opera- 
tions. For this reason, adjustments can be made to the fixed 
rates used in this report for specific known rates at in- 
dividual operations. 



COST DATE ADJUSTMENTS 

All cost equations were calculated in January 1985 
dollars. Costs calculated for any particular cost item are 
broken down into specific categories and subcategories to 
facilitate adjustment to specific dates. These include 
Labor. 

1. Mine labor. 

2. Processing labor. 

3. Repair labor. 
Equipment. 

1. Equipment and equipment parts. 

2. Fuel and lubrication. 

3. Electricity. 

4. Tires. 
Supplies. 

1. Steel items. 

2. Explosives. 

3. Timber. 

4. Construction materials. 

5. Industrial materials. 

For placer mining, most general maintenance and non- 
overhaul repairs are accomplished by the equipment 
operator, so repair labor rates are assumed to be equal to 
those of the operator. If information available to the 
evaluator indicates that this is not the case, repair labor 



16 



portions of the total labor cost are stated to facilitate 
adjustment. 

Equipment operating costs are broken down into respec- 
tive percentages contributed by parts, fuel and lubrication, 
electricity, and tires. These percentages, listed immediately 
following the cost equations, are used to calculate specific 
costs for each subcategory so that they may be updated. 
Supply costs are broken down and handled in a similar 
manner. 

Cost date indexes for the preceding subcategories are 
provided in table 4. These and other cost indexes are up- 
dated every 6 months and are available from the Bureau 
of Mines, Western Field Operations Center, East 360 Third 
Avenue, Spokane, WA 99202. To adjust a cost to a specific 
date, divide the index for that date by the index for January 
1985, and multiply the resulting quotient by the cost 
calculated for the respective subcategory. An example of 
such an update follows. 

Example Cost Update 

Calculate the cost in July 1985 dollars of extracting and 
moving pay gravel 300 ft over level terrain using bulldozers. 
Assume a 200-LCY/h operation, and use the operating cost 
equations provided in the operating costs— mining- 
bulldozers portion of section 2. 



Operating costs per LCY 
(from section 2): 

Equipment operating cost 0.993(200)"° 43 ° 

Labor operating cost 14.01 (200)"° 945 

January 1 985 total 



Subcategory costs per LCY 
(from section 2): 

Equipment parts 

Fuel and lubrication 

Operator labor 

Repair labor 



0.47 
0.53 
0.86 
0.14 



$0,102 
$0,102 
$0,094 
$0,094 



$0,102 
.094 
.196 



$0,048 
$0,054 
$0,081 
$0,013 



Update indexes 



Subcategory July 85/Jan. 85 Quotient 



(from table 4): 

Equipment parts Equipment 

Fuel and lubrication . Fuel 

Operator labor Mine labor 

Repair labor Mine labor 

Updated costs per LCY: 

Equipment parts 

Fuel and lubrication 

Operator labor 

Repair labor 

July 1985 total cost per LCY. 



362.3/360.4 

630.7/636.2 

$11.98/$11.69 

$11.98/$11.69 



1.005 x $0,048 
0.991 x $0,054 
1.025 x $0,081 
1.025 x $0,013 



1.005 
0.991 
1.025 
1.025 



$0,048 
.054 
.083 
.013 

.198 



SITE ADJUSTMENT FACTORS 

As stated earlier, adjustment factors determine the 
precision for cost estimates and must be used carefully. 
Several factors are provided for each curve, and their use 



will significantly alter the calculated cost. The following 
example illustrates factor use. 

Example Adjustment Factor Application 

Calculate the cost of extracting pay gravel in a hard dig- 
ging situation and moving it 800 ft up an 8% gradient us- 
ing bulldozers. Assume a 200-LCY/h operation (January 
1985 dollars), and use the operating cost and adjustment 
factor equations provided in the operating costs— mining- 
bulldozers portion of section 2. 

Operating costs per LCY 
(from section 2): 

Equipment operating cost 0.993(200)"° 43 ° = $0,102 

Labor operating cost 14.01 (200)"° 945 = .094 

January 1985 total 196 

Factors (from section 2): 

Distance F = 0.00581(800)° 9 ° 4 = 2.447 

Gradient F c = i.041el°° 15 < 80) l = 1.174 

Digging difficulty 1 .670 

Used equipment: 

Equipment U„ = 1 .206(200)"° ° 13 = 1.126 

Labor U, = 0.967(200)° ° 15 = 1 .047 

Factored cost per LCY: 
From total cost equation 
for bulldozers: 

[$0,102(1.126) + $0,094(1.047)] x 2.447 x 1.174 x 1.670 = 

January 1985 total cost per LCY $1 .023 

The 500% increase in operating cost, from $0,196 to 
$1,023 per loose cubic yard, demonstrates the dramatic ef- 
fect of using the proper factors. If a cost category contains 
a factor not applicable to the deposit in question, then 
simply leave that factor out of the total cost equation. 

The variables inserted in the factor equations are 
generally self-evident. An exception to this is the digging 
difficulty factor. Parameters for this factor are based on the 
following: 

1. Easy digging.— Unpacked earth, sand, and gravel. 

2. Medium digging.— Packed earth, sand, and gravel, dry 
clay, and soil with less than 25% rock content. 

3. Medium to hard digging.— Hard packed soil, soil with 
up to 50% rock content, and gravel with cobbles. 

4. Hard digging.— Soil with up to 75% rock content, gravel 
with boulders, and cemented gravels. 

It can be seen from these parameters that many deposits 
will fall into one of the last two categories. Digging difficulty 
has a dramatic effect on the cost of extraction, so these fac- 
tors must be chosen carefully. 

Bulldozer and backhoe curves both contain a digging 
difficulty factor. Other excavation equipment, such as 
draglines, scrapers, and front-end loaders, are generally 
suited for special digging conditions and are not used in 
harder ground. Consequently, no digging difficulty factor 
is provided for these. 



17 



Table 4.— Cost date indexes 1 



Mining 
labor 2 



Equip- 
ment and 
repair 
parts 



Fuel 

and 

lubrication 



Elec- 
tricity 



Tires 



Bits 
and 
steel 



Explo- 
sives 



Tim- 
ber 



Construc- 
tion ma- 
terial 3 



1 Unless otherwise noted, based on U.S. Bureau of Labor Statistics (BLS) "Producer Price Indexes,' 

2 Based on BLS "Employment and Earnings: Average Hourly Earnings, Mining." 

3 Based on Engineering and News Record "Market Trends: Building Cost." 

4 January. 

5 July. 

6 January (base cost year for this report). 



base year 1967 



100. 



Indus- 
trial 
material 



1960 . 


$2.61 


85.8 


95.5 


100.1 


113.1 


97.1 


94.5 


92.1 


99 


95.3 


1961 . 


2.64 


87.3 


97.2 


100.7 


109.9 


97.2 


97.0 


87.4 


97 


94.8 


1962 . 


2.70 


87.5 


96.1 


101.9 


94.7 


95.8 


97.0 


89.0 


96 


94.8 


1963 . 


2.75 


89.0 


95.1 


101.1 


96.9 


95.7 


100.4 


91.2 


98 


94.7 


1964 . 


2.81 


91.2 


90.7 


100.3 


97.6 


97.0 


100.0 


92.9 


98 


95.2 


1965 


2.92 


93.6 


92.8 


100.3 


98.8 


97.9 


99.6 


94.0 


97 


96.4 


1966 . 


3.05 


96.5 


97.4 


99.8 


101.3 


98.7 


98.1 


100.1 


99 


98.5 


1967 . 


3.19 


100.0 


100.0 


100.0 


100.0 


100.0 


100.0 


100.0 


100 


100.0 


1968 . 


3.35 


105.7 


98.1 


100.9 


102.7 


101.9 


102.3 


117.4 


127 


102.5 


1969 . 


3.61 


110.4 


99.6 


102.2 


98.3 


107.0 


104.7 


131.6 


108 


106.0 


1970 . 


3.85 


115.9 


101.0 


106.6 


105.4 


115.1 


106.7 


113.7 


109 


110.0 


1971 . 


4.06 


121.4 


106.8 


115.5 


110.3 


121.8 


113.3 


135.5 


133 


114.0 


1972 . 


4.41 


125.7 


108.9 


123.9 


111.3 


128.4 


115.2 


159.4 


151 


117.9 


1973 . 


4.73 


130.7 


128.6 


132.6 


115.7 


136.2 


120.1 


205.2 


154 


125.9 


1974 . 


5.21 


152.3 


223.4 


172.3 


141.6 


178.6 


150.0 


207.1 


167 


153.8 


1975 . 


5.90 


185.2 


257.5 


209.7 


155.4 


200.9 


178.0 


192.5 


186.3 


171.5 


1976 . 


6.42 


198.9 


276.6 


226.7 


172.8 


215.9 


187.2 


233.0 


205.5 


182.4 


1977 . 


6.88 


213.7 


308.1 


257.0 


181.5 


230.3 


193.1 


276.5 


237.7 


195.1 


1978 . 


7.67 


232.8 


321.0 


279.5 


192.0 


253.5 


208.7 


322.1 


247.7 


209.4 


1979 . 


8.50 


256.2 


444.8 


305.3 


219.6 


283.5 


225.6 


354.3 


269.28 


236.5 


1980" 


8.70 


275.4 


582.4 


334.8 


236.9 


297.3 


237.1 


336.3 


280.86 


260.3 


1980s 


9.08 


290.9 


693.3 


376.0 


250.4 


300.4 


254.4 


327.3 


289.05 


275.6 


1981" 


9.78 


304.9 


736.0 


393.9 


256.2 


322.8 


268.5 


331.6 


298.25 


289.9 


1981 s 


10.07 


324.0 


818.4 


429.9 


269.6 


338.7 


292.8 


330.1 


312.11 


306.0 


1982 4 


10.58 


337.0 


802.9 


454.0 


271.6 


343.1 


293.2 


310.6 


324.74 


311.7 


1982 s 


10.91 


346.1 


777.1 


471.5 


272.6 


337.4 


294.8 


319.2 


330.56 


313.0 


1983" 


11.10 


348.6 


727.1 


482.6 


285.4 


333.2 


300.4 


324.2 


342.01 


314.0 


1983 5 


11.31 


352.7 


694.9 


492.2 


256.6 


341.3 


302.8 


372.5 


357.28 


316.6 


1984 4 


11.56 


354.3 


669.7 


492.0 


258.0 


354.1 


301.3 


353.2 


355.52 


319.2 


19845 


11.62 


358.2 


674.6 


525.5 


256.3 


357.2 


312.4 


343.3 


357.90 


324.0 


1985 6 


11.69 


360.4 


636.2 


524.9 


262.0 


357.4 


313.4 


343.2 


358.32 


323.2 


1985 5 


11.98 


362.3 


630.7 


540.3 


246.0 


354.6 


312.1 


354.9 


363.63 


324.3 



LABOR RATES 

The cost of labor in placer mining is highly variable and 
cannot be precisely estimated in every case. For the pur- 
poses of this report, only two separate labor rates are used: 
$15.69/h for mining functions, and $15.60/h for milling. 
These rates apply to operation, maintenance, installation, 
and construction labor. The labor portions of each specific 
cost category are broken out and in this way can be adjusted 
to the estimator's particular labor rate. To accomplish this, 
multiply the labor cost for each category by the ratio of 
desired labor rate to mining or milling labor rate ($15.69/h 
or $15.60/h). The following example illustrates this 
adjustment. 

Example Labor Rate Adjustment 

Calculate the cost of extracting and moving pay gravel 
300 ft over level terrain using bulldozers with an operator 
labor cost of $18.00/h. Assume a 200-LCY/h operation 
( January 1985 dollars), and use the operating cost equations 
provided in the operating costs— mining-bulldozers portion 
of section 2. 



Operating costs per LCY 
(from section 2): 

Equipment operating cost 0.993(200)"° 430 

Labor operating cost 14.01(200)° 945 

January 1985 total 



Labor adjustment: 
Labor operating cost per 
LCY ($1 8.00/$1 5.69) x $0,094 

Adjusted cost per LCY: 

Equipment operating cost 

Labor operating cost 

January 1985 total cost per LCY 



$0,102 
.094 
.196 



.108 



.102 
.108 



.210 



Labor rates are based on wage scales for the western 
United States (including Alaska) and include a 24% burden. 
This burden consists of 9.8% workers compensation in- 
surance, 7.0% Social Security tax, 3.7% State unemploy- 
ment insurance, and 3.5% Federal unemployment tax. If 
other costs such as health and retirement benefits are to 
be included, they must be added to an estimated labor rate. 

To familiarize the reader with the use of this cost 
estimating system, an example of a complete cost estimate 
is included in the appendix. 



is 



FINANCIAL ANALYSIS 



The purpose of this report is to provide an estimate of 
capital and operating costs for small placer mines. A distinc- 
t ion must be made between a cost estimate and an economic 
feasibility analysis. Capital and operating costs are simply 
two separate variables in a complete economic analysis. To 
determine the economic feasibility of an operation, the 
evaluator must consider each of the following: 

1. Recoverable value of commodity. 

2. Local, State, and Federal taxes. 

3. Capital depreciation. 

4. Depletion allowances. 

5. Desired return on investment. 

6. Costs and methods of project financing. 

7. Inflation. 

8. Escalation. 

9. Environmental intangibles. 

Economic feasibility analysis is a subject in itself, and 
will not be covered here. The preceding list is included to 
emphasize the following: A prospect is not economically 
feasible simply because the apparent commodity value ex- 
ceeds the total capital and accrued operating costs calculated 
from this manual. 

The costs associated with the preceding list are real and 
must be considered when determining the feasibility of a 
prospect. Any attempt to provide guidelines for determina- 
tion of feasibility based solely on estimates of capital and 



operating costs would be highly misleading. There is no 
quick and easy way to account for the wide variety of situa- 
tions encountered in economic analysis. Each one of the 
preceding items must be examined individually to provide 
accurate economic feasibility estimates, and a complete 
cash-flow analysis is the only way to ensure that proper 
results are obtained. To accomplish this, all yearly income 
and expenses must be tabulated. Then the rate of return 
over time must be calculated from the resultant profits or 
losses. The evaluator must consider all factors influencing 
income and include all expenses as well as account for the 
value of money over time and choose an acceptable rate of 
return. 

In brief, the operator will have to receive adequate 
revenues from commodities recovered to 

1. Cover all operating expenses. 

2. Recover initial equipment expenditures. 

3. Provide for equipment replacement. 

4. Cover all exploration and development costs. 

5. Pay taxes. 

6. Compensate for inflation and cost escalation. 

7. Supply a reasonable profit. 

Only when enough revenue is produced to cover all of 
the above can an operation be considered economically 
feasible. 



BIBLIOGRAPHY 



Adorjan, L.A. Mineral Processing. Paper in Mining Annual 
Review 1984. Min. J. (London), 1984, pp. 217-219. 

Bertoldi, M.J. Preliminary Economics of Mining a Thick Coal 
Seam by Dragline, Shovel-Truck, and Scraper Mining Systems. 
BuMines IC 8761, 1977, 27 pp. 

Daily, A. Valuation of Large, Gold-Bearing Placers. Eng. and Min. 
J., v. 163, No. 7, July 1962, pp. 80-88. 

Earll, F.N., K.S. Stout, G.G. Griswald, Jr., R.I. Smith, F.H. Kelly, 
D.J. Emblen, W.A. Vine, and D.H. Dahlem. Handbook for Small 
Mining Enterprises. MT Bur. Mines and Geol. Bull. 99, 1976, 218 
pp. 

Gardner, E.D., and P.T. Allsman. Power-Shovel and Dragline 
Placer Mining. BuMines IC 7013, 1938, 68 pp. 

Jarrett, B.M. Development Document for Final Effluent Limita- 
tions Guidelines and New Source Performance Standards for the 
Ore Mining and Dressing Point Source Category. U.S. EPA Docu- 
ment 440/1-82/061, 1982, 656 pp. 

Levell, J.H., V.V. Thornsberry, W.G. Salisbury, and D.A. Smith. 
1983 Mineral Resource Studies: Kantishna Hills and Dunkle Mine 
Areas, Denali National Park and Preserve, Alaska. Volume II. Ap- 
pendix A (contract S0124031, Salisbury & Dietz, Inc.). BuMines 
OFR 129(2)-84, 1984, pp. 1-232. 

Macdonald, E.H. Alluvial Mining: The Geology, Technology, and 
Economics of Placers. Chapman and Hall (London), 1983, 508 pp. 



McLellan, R.R., R.D. Berkenkotter, R.C. Wilmot, and R.L. Stahl. 
Drilling and Sampling Tertiary Gold-Bearing Gravels at Badger 
Hill, Nevada County, Calif. BuMines RI 7935, 1974, 50 pp. 

Schumacher, O.L. Placer Gold— Production and Cost History of 
an Alaska Placer Gold Mine. Western Mine Eng.— Min. Cost Serv- 
ice reprint, Spokane, WA, 1985, 5 pp. 

Sharp, A. P., and A.D. Cook. Safety Practices in Churn Drilling 
at Morenci Branch, Phelps Dodge Corp., Morenci, Ariz. BuMines 
IC 7548, 1950, 22 pp. 

Stout, K.S. The Profitable Small Mine, Prospecting to Operation. 
McGraw-Hill, 1984, pp. 83-98. 

Taggart, A.F. Ores and Industrial Minerals. Sec. 11 in Handbook 
of Mineral Dressing. Wiley, 1945, 140 pp. 

Terrill, I. J., and J.B. Villar. Elements of High-Capacity Gravity 
Separation. CIM Bull, v. 68, No. 757, May 1975, pp. 94-101. 

Thoenen, J.R., and E.J. Lintner. Churn-Drill Performance. 
BuMines RI 4058, 1947, 48 pp. 

Thomas, B.I., D.J. Cook, E. Wolff, and W.H. Kerns. Placer Min- 
ing in Alaska: Methods and Costs at Operations Using Hydraulic 
and Mechanical Excavation Equipment With Non-Floating 
Washing Plants. BuMines IC 7926, 1959, 34 pp. 

West, J.M. How To Mine and Prospect for Placer Gold. BuMines 
IC 8517, 1971, 43 pp. 

Wilson, E.D. Gold Placers and Placering in Arizona. AZ Bur. Geol. 
and Min. Tech. Bull. 168, 1961, 124 pp. 



19 



SECTION 2.— COST ESTIMATION 



CAPITAL AND OPERATING COST CATEGORIES 



Section 2 contains equations for estimating capital and 
operating costs associated with placer mining. Equations 
are provided for the following items. 



Capital costs: 


Operating costs: 


Exploration: 


Overburden removal: 


Panning 


Bulldozers 


Churn drilling 


Draglines 


Bucket drilling 


Front-end loaders 


Trenching 


Rear-dump trucks 


General 


Scrapers 


reconnaissance 


Mining: 


Camp costs 


Backhoes 


Seismic surveying 


Bulldozers 


Rotary drilling 


Draglines 


Helicopter rental 


Front-end loaders 


Development: 


Rear-dump trucks 


Access roads 


Scrapers 


Clearing 


Processing: 


Preproduction 


Conveyors 


overburden removal: 


Feed hoppers 


Bulldozers 


Jig concentrators 


Draglines 


Sluices 


Front-end loaders 


Spiral concentrators 


Rear-dump trucks 


Table concentrators 


Scrapers 


Tailings removal: 


Mine equipment: 


Bulldozers 


Backhoes 


Draglines 


Bulldozers 


Front-end loaders 


Draglines 


Rear-dump trucks 


Front-end loaders 


Scrapers 


Rear-dump trucks 


Trommels 


Scrapers 


Vibrating screens 


Processing equipment: 


Supplemental: 


Conveyors 


Employee housing 


Feed hoppers 


Generators 


Jig concentrators 


Lost time and general 


Sluices 


services 


Spiral concentrators 


Pumps 


Table concentrators 




Trommels 




Vibrating screens 




Supplemental: 




Buildings 




Employee housing 




Generators 




Pumps 




Settling ponds 





Included in this section are summary forms (figs. 4-6) 
that may be used to aid in total capital and operating cost 
calculations. A bibliography of cost information sources is 
provided at the end of this section. 

The appendix contains a complete sample cost estima- 
tion. This sample will familiarize the reader with cost 
estimation techniques used in this report. 



20 



CAPITAL COSTS 



EXPLORATION 



Two methods are presented for calculating exploration 
o»t.- Method l allows tlie e\aluator to roughly estimate 
costs with a minimum of information. Method 2 requires 
a detailed exploration plan and provides the user with a 
much more precise cost. 

Method 1: If information concerning exploration of a 
deposit is not available, the following equation may be 
used to estimate an exploration capital cost. It must be em- 
phasized, however, that costs calculated from this equation 
can be very misleading, and it is recommended that a de- 
tailed exploration program be designed if possible and that 
costs be assigned using method 2. 

As stated in section 1, the amount of exploration re- 
quired is a highly variable function of many factors. This 
equation is based on estimated exploration costs for several 
successful placer operations, but these deposits may have 
little in common with the one being evaluated. 

The base equation is applied to the following variable: 

X == Total estimated resource, in bank cubic yards 
(BCY) 

Base Equation: 

Exploration capital costs . .Y c = 0.669(X) 0849 



































































































































00,000 
































































































































































10,000 
































































































































































1 ,000 
































10, 


300 






100 


000 




1 


,000,000 




10, ( 


XX 



TOTAL RESOURCE, bank cubic yards 



Exploration capital costs 



An exact breakdown of expenses included in this cost 
is not available. In general, exploration is a labor-intensive 
task. Unless the deposit is extremely remote, a large share 
of the exploration cost will be attributed to labor. If the 
deposit is remote, costs of access equipment (helicopters, etc.) 
will become a factor. 



Method 2: Excellent cost data for most exploration func- 
tions may be found in the Bureau's Cost Estimation System 
(CES) Handbook (IC 9142). Functions covered in that 
publication include 

Helicopter rental rates. 

Sample preparation and analysis costs. 

Drill capacities and costs for core, rotary, and 
hammer drills. 

Survey charges. 

Labor rates. 

Travel costs. 

Ground transportation costs. 

Field equipment costs. 

Geological, geophysical, and geochemical exploration 
technique costs. 

Costs directly related to placer mining from the above 
list are summarized in the following tabulations. Several 
items particular to placer mining are not covered in the CES 
Handbook. These items, for which costs follow, include 

Panning. 

Churn drilling. 

Bucket drilling. 

Trenching. 



CAPITAL COSTS 



21 



Exploration Cost Tabulations: As in the CES Hand- 
book, costs are given in dollars per unit processed (cubic 
yard, sample, foot drilled, etc.). The product of the unit cost 
and the total units processed constitutes the total capital 
cost for any particular method of exploration. Total explora- 
tion costs consist of the sum of these individual exploration 
method expenses. A summary sheet for these calculations 
is shown in figure 4. 

EXPLORATION-PANNING 

Average cost per sample $2.10 

Cost range $1.90-$2.60 

Cost variables Labor efficiency and 

material being panned. 

EXPLORATION-CHURN DRILLING 

Average cost per foot $45 

Cost range $20-$70 

Cost variables Depth of hole, material 

being drilled, site access, 
and local competition. 

EXPLORATION-BUCKET DRILLING 

Average cost per foot $9.20 

Cost range $5-$20 

Cost variables Depth of hole, material 

being drilled, and site 

access. 

EXPLORATION-TRENCHING 

Average cost per cubic yard $7.10 

Cost range $2.25-$28.50 

Cost variables Labor efficiency, material 

being sampled, site 
access, equipment owner- 
ship, sampling method, 
and total volume of work 
to be done. 



CES Exploration Cost Tabulations: Some of the more 
pertinent exploration cost items presented in the CES Hand- 
book (IC 9142) are summarized in the following. A de- 
tailed description of these items can be found in that 
publication. 

EXPLORATION-GENERAL RECONNAISSANCE 

Average cost per worker-day $195 

Cost range $175-$210 

Cost variables Deposit access, terrain, 

and labor efficiency. 

EXPLORATION-CAMP COSTS 

Average cost per worker-day $30 

Cost range $19-$41 

Cost variables Deposit remoteness, 

terrain, access, and 

climate. 

EXPLORATION-SEISMIC SURVEYING (REFRACTION) 

Average cost per linear foot $1.50 

Cost range $1.00-$2.50 

Cost variables Labor efficiency, deposit 

access, and terrain. 

EXPLORATION-ROTARY DRILLING 

Average cost per foot $6.50 

Cost range $2.00-$11.50 

Cost variables Depth of hole, material 

being drilled, and site 

access. 

EXPLORATION-HELICOPTER RENTAL 

Average cost per hour $395 

Cost range $305-$590 

Cost variables Passenger capacity, 

payload capacity, cruise 
speed, and range. 



EXPLORATION COST SUMMARY FORM 



Capital cost calculation: 



General reconnaissance . . worker-days x $ /worker-day 

Camp costs worker-days x $ /worker-day 

Panning samples x $ /pan 

Churn drilling ft drilled x $ /ft 

Bucket drilling ft drilled x $ /ft 

Trenching yd 3 x $ /yd 3 

Seismic surveying linear ft x $ /linear ft 

Rotary drilling ft drilled x $ /ft 

Helicopter time h x $ /h 

x$ / 

x$ / 

x$ / 

x $ / 

x$ / 

x$ / 

x$ / 

x$ / 

Total 



Figure 4.— Exploration cost summary form. 



■22 



CAPITAL COSTS 



DEVELOPMENT— ACCESS ROADS 



Capital Cost Equation: This equation provides the cost 
per mile of road construction to the deposit and between 
various facilities. Costs include clearing and excavation, but 
do not account for any blasting or gravel surfacing that may 
be required. The equation is applied to the following 
variable: 

X = Average width of roadbed, in feet. 

The following assumptions were made in estimating road 

costs: 

1. Side slope, 25 r /i. 3. Moderate digging 

2. Moderate ground cover. difficulty. 



100,000 



Base Equation: 

Access road capital cost 



.Y c = 765.65(X)°- 922 



The capital cost consists of 68% construction labor, 13% 
parts. I6 r /f fuel and lubricants, and 3% tire replacement. 

Brush Factor: The original equation is based on the 
assumption that ground cover consists of a mixture of brush 
and trees. If vegetation is light (i.e., consisting mainly of 
brush or grasses), the total cost per mile (covered with brush) 
must be multiplied by the factor obtained from the follow- 
ing equation: 

F B = 0.158(X) 0325 . 

Forest Factor: If ground cover is heavy (i.e., consisting 
mainly of trees), the total cost per mile (covered with trees) 
must be multiplied by the factor obtained from the follow- 
ing equation: 

F F = 2.000(X)-° 079 . 

Side Slope Factor: If average side slope of the terrain 
is other than 25%, the factor obtained from the following 
equation must be applied to the total cost per mile: 

P _ Q 633gl0. 021 (percent slope)] 

Surfacing Factor: If gravel surfacing is required, the 
cost per mile must be multiplied by the following factor to 
account for the additional labor, equipment, and supply 
costs: 

F G = 6.743. 

Blasting Factor: In hard-rock situations, blasting may 
be required. Should this be the case, the cost obtained from 
the following equation must be added to total access road 
cost. 



o 10,000 



1 ,000 



100 



AVERAGE ROADBED WIDTH, feet 
Development capital costs - Access roads 



F H = [12,059. 18(X) 0534 ] x [miles of roadbed requiring 
blasting]. 

Total Cost: Access road capital cost is determined by 

[(Y c x F B x F F x F s x F G ) x total miles] + F H . 



This total cost is then entered in the appropriate row of the 
tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



23 



DEVELOPMENT— CLEARING 



Capital Cost Equation: This equation provides the 
total capital cost of clearing brush and timber from the sur- 
face of a deposit prior to mining. Costs include labor, equip- 
ment, and supplies required to completely strip the surface 
of growth, and to dispose of debris. The equation is applied 
to the following variable: 

X = Total acreage to be cleared. 

The following assumptions were made in estimating 
clearing costs: 

1. Level slope. 2. Moderate ground cover. 

Base Equation: 

Clearing capital cost Y c = 1,043.61(X) 0913 

The capital cost consists of 68% construction labor, 18% fuel 
and lubricants, 12% parts, and 2% steel supplies. 

Slope Factor: The original equation is based on the 
assumption that the slope of the surface overlying the 
deposit is nearly level. If some slope is present, the factor 
obtained from the following equation must be applied to the 
clearing capital cost: 

F = 942e' 0008(percent sl °P e " 

Brush Factor: Ground cover is assumed to consist of 
a mixture of brush and small trees. If the surface is covered 
with only brush and grasses, the following factor must be 
applied to the cost: 

F B = 0.250. 

Forest Factor: If the surface is forested, capital cost 
must be multiplied by the following factor: 

F F = 1.750. 

Total Cost: Clearing capital cost is determined by 

(Y„ x Fo x F„ x F ) 

v C S B x F'- 

This total cost is then entered in the appropriate row of the 
tabulation shown in figure 5 for final capital cost 
calculation. 



* ' 
































































































































10 

□ 1 00 000 

































































































T3 
































h- 
m 

D 
































cr 
- 
































































































































































i . nnn 

































10 100 

TOTAL SURFRCE RRER, acres 

lopment capital costs - Clearing 



,000 






24 



CAPITAL COSTS 



PREPRODUCTION OVERBURDEN REMOVAL— BULLDOZERS 



Capital Cost Equations: These equations provide the 
cost of excavating and relocating overburden using 
bulldozers. Costs are reported in dollars per loose cubic yard 
of overburden handled. The equations are applied to the 
following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by bulldozer. 

The base equations assume the following: 

1. No ripping. 4. Dozing distance, 300 ft. 

2. Cutting distance, 5. Average operator ability. 

50 ft. 6. Nearly level gradient. 

3. Efficiency, 50 min/h. 



Base Equations: 

Equipment operating cost Y E 



0.993(X)-°- 430 



Labor operating cost 



Y L = 14.0KX)- 0945 



Equipment operating costs average 47% parts and 53% fuel 
and lubrication. Labor operating costs average 86% operator 
labor and 14% repair labor. 

Distance Factor: If the average dozing distance is other 
than 300 ft, the factor obtained from the following equa- 
tion must be applied to total cost per loose cubic yard: 

F D = 0.00581(distance) 0904 . 

Gradient Factor: If the average gradient is other than 
level, the factor obtained from the following equation must 
be applied to the total cost per loose cubic yard: 

F = 1 041e'°- 015 ' pera ' m K 1 ' adient, l 

Ripping Factor: If ripping is required, total operating 
cost must be multiplied by the following factor, this will 
account for reduced productivity associated with ripping: 

F D = 1.595. 



0. 100 









































































































































^s. Equipment 




































^ Labor 

























10 100 1,000 

CAPACITY, maximum loose cubic yards par hour 

Overburden removal capital costs - Bulldozers 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 



Equipment factor U e 

Labor factor U, 



1.206(X)- 0013 
0.967(X) 0015 



Digging Difficulty Factor: Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required. 
If so, one of the following should be applied to total cost per 
loose cubic yard: 



easy digging 
medium 



.0.830 F u , medium-hard 



digging 1.250 



digging 1.000 F H , hard digging . . . 1.670 



Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e ) + Y L (U,)] x F D x F G x F H x Fr . 

To obtain overburden removal capital cost, the total cost 
per loose cubic yard must be multiplied by total amount 
of overburden handled by bulldozer prior to production. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



25 



PREPRODUCTION OVERBURDEN REMOVAL— DRAGLINES 



Capital Cost Equations: These equations provide the 
cost of excavating overburden using draglines. Costs are 
reported in dollars per loose cubic yard of overburden han- 
dled. The equations are applied to the following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by dragline. 

The base curves assume the following: 



I .000 



Base Equations: 

Equipment operating costs.. x E 

Labor operating costs Y L = 12.19(X)-° 888 



Y E = 1.984(X)-°- 390 



Equipment operating costs consist of 67% parts and 33% 
fuel and lubrication. Labor operating costs consist of 78% 
operator labor and 22% repair labor. 

Swing Angle Factor: If the average swing angle is 
other than 90°, the factor obtained from the following equa- 
tion must be applied to the total cost per loose cubic yard: 

F s = 0.304 (swing angle) 0269 . 



1. Bucket efficiency, 0.90. 


3. Swing angle, 90°. 


(0 0.100 
a 


2. Full hoist. 


4. Average operator 







ability. 













































































^*"*-» Equipment 
























































^ Lctoor 



































































10 100 1,000 

CAPACITY, maximum loose cubic yards per hour 

Overburden removal capital costs - Draglines 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by factors obtained from the following equations: 



Equipment factor U 

Labor factor U, 



= 1.162(X)-°- 017 
= 0.989(X) 0006 



Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e ) + Y L (U,)] x F s . 

To obtain the overburden removal capital cost, the total cost 
per loose cubic yard must be multiplied by the total amount 
of overburden handled by dragline prior to production. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 5 for final capital cost 
calculation. 



26 



CAPITAL COSTS 



PREPRODUCTION OVERBURDEN REMOVAL— FRONT-END LOADERS 



Capital Cost Equations: These equations provide the 
cost of relocating overburden using wheel-type front-end 
loaders. Costs are reported in dollars per loose cubic yard 
of overburden handled. The equations are applied to the 
tol lowing variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by front-end loader. 

The base equations assume the following: 

1. Haul distance, 500 ft. 3. Inconsistent operation. 

2. Rolling resistance, 4. Wheel-type loader, 
nearly level gradient. 



1 .000 



Base Equations: 

Equipment operating cost 
Labor operating cost . . . . 



Y E = 0.407(X)-0-225 
Y L = 13.07(X)-°936 



Equipment operating costs average 22% parts, 46% fuel and 
lubrication, and 32% tires. Labor operating costs average 
90% operator labor and 10% repair labor. 

Distance Factor: If the average haul distance is other 
than 500 ft, the factor obtained from the following equa- 
tion must be applied to the total cost per loose cubic yard: 



» . 1 00 

































































































Equ 1 pmen t 


























































Labor 















































10 100 1,000 

CRPRCITY, maximum loose cubic yards per hour 

Overburden removal capital costs - Front-end loaders 



F D = 0.023(distance) 0616 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%-, the factor obtained from 
the following equation must be applied to the total cost per 
loose cubic yard: 



F (i = 



0.877e IOO46l P elct ' nt Biadicnt)|_ 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e = 1.162(X)-0-° 17 

Labor factor U, = 0.989(X)°°°6 

Track-Type Loader Factor: If track-type loaders are 
used, the following factors must be applied to the total cost 
obtained from the base equations: 

Equipment factor T e = 1.378 

Labor factor T, = 1.073 

Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e ) (T e ) + Y L (U,) (T,)] x F D x F G . 



To obtain the overburden removal capital cost, the total cost 
per loose cubic yard must be multiplied by the total amount 
of overburden handled by front-end loader prior to produc- 



tion. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 5 for final 
capital cost calculation. 



CAPITAL COSTS 



27 



PREPRODUCTION OVERBURDEN REMOVAL— REAR-DUMP TRUCKS 



Capital Cost Equations: These equations provide the 
cost of hauling overburden using rear-dump trucks. Costs 
are reported in dollars per loose cubic yard of overburden 
handled. The equations are applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, 

overburden, and tails moved hourly by rear- 
dump truck. 

The base equations assume the following: 

1. Haul distance, 2,500 ft. 4. Average operator 

2. Loader cycles to fill, 4. ability. 

3. Efficiency, 50 min/h. 5. Rolling resistance, 2%, 

nearly level gradient. 

Base Equations: 

Equipment operating costs . . Y E = 0.602(X)-0-296 
Labor operating cost Y L = 11.34(X)-°89i 

Equipment operating costs consist of 28% parts, 58% fuel 
and lubrication, and 14% tires. Labor operating costs con- 
sist of 82% operator labor and 18% repair labor. 

Distance Factor: If average haul distance is other than 
2,500 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F D = 0.093(distance)0-3". 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to the total cost per 
loose cubic yard: 

f = 0.907e[°' 049, P ercent gradient)I_ 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e = 0.984(X)°°ie 

Labor factor U, = 0.943(X)°-°2i 

Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e ) + Y L (U,)] x F D x F G . 



O.QIO 





















































































































~~"* Equipment 


































\ Labor 













































10 100 I ,000 

CRPRCITY, maximum I oosa cubic yards per hour 

Overburden removal capital costs - Rear-dump trucks 



To obtain the overburden removal capital cost, the total cost 
per loose cubic yard must be multiplied by the total amount 
of overburden handled by truck prior to production. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 5 for final capital cost 
calculation. 



28 



CAPITAL COSTS 



PREPRODUCTION OVERBURDEN REMOVAL— SCRAPERS 



Capital Cost Equations: These equations provide the 
cost of excavating and hauling overburden using scrapers. 
Costs are reported in dollars per loose cubic yard of over- 
burden handled. The equations are applied to the follow- 
ing variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by scraper. 



I .000 



The base curves assume the following: 

Standard scrapers. 4. Average haul distance, 
Rolling resistance, 6%, 1,000 ft. 

nearly level gradient. 5. Average operator 
Efficiency, 50 min/h. ability. 



Base Equations: 

Equipment operating cost. .Y E 
Labor operating cost Y L 



0.325(X)-"-2io 
12.01(X)-0-93o 



Equipment operating costs consist of 28% parts, 58% fuel 
and lubrication, and 14% tires. Labor operating costs con- 
sist of 82% operator labor and 18% repair labor. 

Distance Factor: If average haul distance is other than 
1,000 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F L) = 0.01947(distance) 0577 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 6%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F, = 0.776e IO047 'p < -' ra ' lU K^dK-ntu 



o.oio 





















































































































"— — Equipment 
























































x LobDr 

























I 00 I , 000 

CAPACITY , maximum loose cubic yards per hour 

Overburden removal capital costs - Scrapers 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e = 1.096(X)-oooe 

Labor factor U, = 0.845(X)°°34 

Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e ) + Y L (U,)] x F D x F G . 



To obtain the overburden removal capital cost, the total cost 
per loose cubic yard must be multiplied by the total amount 
of overburden handled by scraper prior to production. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



29 



MINE EQUIPMENT— BACKHOES 



Capital Cost Equation: This equation furnishes the 
cost of purchasing the appropriate number and size of 
hydraulic backhoes needed to provide the maximum re- 
quired production. Costs do not include transportation, sales 
tax, or discounts. The equation is applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel moved 
hourly by backhoe. 

The following capacities were used to calculate the base 
equation: 



105 hp 95 to 200 

LCY/h 

135 hp 175 to 275 

LCY/h 



195 hp 250 to 375 

LCY/h 

325 hp 350 to 475 

LCY/h 



These capacities are based on the following assumptions: 



Medium digging 

difficulty. 

Average operator 

ability. 

Swing angle, 60° to 

90°. 



4. Maximum digging 
depth, 0% to 50%. 

5. No obstructions. 





































































to 

l_ 

a 






















D 

b 100 000 






















a 






















_l 






















t— 

a. 
cr 












































i n . nnn 























10 1 00 I , 000 

CAPACITY, maximum loose cubic yards per hour 

Mine equipment capital costs - Backhoes 



Base Equation: 

Equipment capital cost . . . Y c = 84,132.01e l000350(X)1 

Equipment capital costs consist entirely of the equipment 
purchase price. 

Digging Depth Factor: If average digging depth is 
other than 50% of maximum depth obtainable for a par- 
ticular make of backhoe, the factor obtained from the follow- 
ing equation must be applied to total capital cost: 

F D = 0.04484(D)°™>, 

where D = percent of maximum digging depth. 

Used Equipment Factor: This factor accounts for the 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

Fu = 0.386. 

Digging Difficulty Factor: Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required. 
If so, one of the following should be applied to total capital 
cost: 

F H , easy digging . . 1.000 F H , medium-hard 

F H , medium digging 1.556 

digging 1.330 F H , hard digging . . 1.822 

Total Cost: Backhoe capital cost is determined by 

Y c x F D x Fu x F H . 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



30 



CAPITAL COSTS 



MINE EQUIPMENT— BULLDOZERS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing the appropriate size and number of 
crawler dozers needed to provide the maximum required 
production. Costs do not include transportation, sales tax, 
or discounts. The equation is applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, 
overburden, and waste moved hourly by 
bulldozer. 

The following capacities were used to calculate the base 
equation: 

65 hp 19.0 LCY/h 

80 hp 31.5 LCY/h 

105 hp 56.5 LCY/h 

140 hp 82.0 LCY/h 



.000,000 



200 hp 126.0 LCY/h 

335 hp 263.5 LCY/h 

460 hp 334.0 LCY/h 

700 hp 497.5 LCY/h 



The above capacities are based on the following 



assumptions: 

1. Straight "S" blades. 

2. No ripping. 

3. Average operator 
ability. 

4. Cutting distance, 
50 ft. 



5. Dozing distance, 
300 ft. 

6. Efficiency, 50 min/h. 

7. Even, nearly level 
gradient. 



10,000 




















































































































































































































100 








.0 



CAPACITY, maximum I oosb cubic yards per hour 



Mine equiment capital costs - Bulldozers 



Base Equation: 

Equipment capital cost. 



.Y c = 3,555.96(X)0 806 



Equipment capital costs consist entirely of equipment pur- 
chase price. 

Distance Factor: If average dozing distance is other 
than 300 ft, the factor obtained from the following equa- 
tion must be applied to capital costs. This will correct for 
the addition or reduction of equipment required to main- 
tain maximum capacity: 

F D = 0.01549(distance)o?32. 



Gradient Factor: If the average gradient is other than 
level, the factor obtained from the following equation must 
be applied to total capital cost. This will correct for the ad- 
dition or reduction of equipment required to maintain max- 
imum capacity. (Favorable haul gradients should be entered 
as negative, uphill haul gradients as positive.) 

P = 1.041e'°' 015, P ercent gradient!) 

Digging Difficulty Factor: Variations from the base 
digging difficulty will necessitate changes in equipment size 
to maintain production capacity. Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required. 
If so, one of the following should be applied to total capital 
cost: 



F H easy digging . . 0.863 

F H medium 

digging 1.000 



digging 1.197 

F H hard digging . . 1.509 



Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

Fu = 0.411. 

Total Cost: Bulldozer capital cost is determined by 

Y c x F H x F D x F G x Fu. 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



31 



MINE EQUIPMENT— DRAGLINES 



Capital Cost Equation: This equation furnishes the 
cost of purchasing the appropriate size dragline needed to 
provide the maximum required production. Costs do not in- 
clude transportation, sales tax, or discounts. The equation 
is applied to the following variable: 

X= Maximum loose cubic yards of pay gravel, 
overburden, and waste moved hourly by 
dragline. 

The following capacities were used to calculate the base 
equation: 

84 hp ... 28 LCY/h 
110 hp. . .47 LCY/h 
148 hp . . . 66 LCY/h 
170 hp. . .75 LCY/h 



I ,000,000 



190 hp . . . 94 LCY/h 
263 hp . . . 132 LCY/h 
289 hp . . . 188 LCY/h 
540 hp . . . 264 LCY/h 



The above capacities are based on the following 
assumptions: 

1. Bucket efficiency, 
0.90. 

2. Full hoist. 



3. Swing angle, 90°. 

4. Average operator 
ability. 



Base Equation: 

Equipment capital cost 



10,000 






10 100 1,000 

CRPflCITY, maximum I oqsq cubic yards per hour 

Mine equipment capital costs - Draglines 



Y c = . 16,606. 12(X)o-678 



Equipment capital costs consist entirely of the equipment 
purchase price. 

Swing Angle Factor: If the average swing angle is 
other than 90 °, the factor obtained from the following equa- 
tion must be applied to total capital cost. This factor will 
compensate for equipment size differences required to ob- 
tain the desired maximum capacity: 

F s = 0.450(swing angle) 180 . 

Used Equipment Factor: This factor accounts for the 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 
Fu = 0.422. 

Total Cost: Dragline capital cost is determined by 
Y r x F s x F„. 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



32 



CAPITAL COSTS 



MINE EQUIPMENT— FRONT-END LOADERS 



Capital Cost Equation: This equation provides the cost 
of purchasing the appropriate size and number of wheel- 
type front-end loaders needed to supply the maximum re- 
quired production. Costs do not include transportation, sales 
tax, or discounts. The equation is applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, 
overburden, and waste moved hourly by 
front-end loader. 

The base equation was calculated using the following 



capacities: 




1.00-yd 3 bucket, 


3.50-yd 3 bucket, 


65 hp 24.00 LCY/h 


200 hp . . 129.50 LCY/h 


1.50-yd 3 bucket, 


4.50-yd 3 bucket, 


80 hp .... 34.50 LCY/h 


270 hp . .171.00 LCY/h 


1.75-yd 3 bucket, 


6.50-yd 3 bucket, 


105 hp . . . 38.50 LCY/h 


375 hp . .234.00 LCY/h 


2.25-yd 3 bucket, 


12.00-yd 3 bucket, 


125 hp .. .56.25 LCY/h 


690 hp . .348.00 LCY/h 


2.75-yd 3 bucket, 




155 hp . . .66.00 LCY/h 







































































ID 

L 

a 
























w 100 000 






















o 






















_i 


































































10 000 






















1 


a 








100 








1,0 



CAPACITY, maximum loose cubic yards per hour 



Mine equipment capital costs - Front-end loaders 



The above capacities are based on the following 
assumptions: 



1. Haul distance, 500 ft. 4. 

2. Rolling resistance, 2%, 5. 
nearly level gradient. 6. 

3. Inconsistent 
operation. 



Wheel-type loader. 
Efficiency, 50 min/h. 
General purpose 
bucket, heaped. 



Base Equation: 

Equipment capital cost. . .Y c = 2,711. 10(X)° - 896 

Equipment capital costs consist entirely of the equipment 
purchase price. 

Distance Factor: If the average haul distance is other 
than 500 ft, the factor obtained from the following equa- 
tion must be applied to the capital cost. This will correct 
for the addition or reduction of equipment required to main- 
tain maximum capacity. (If tracked loaders are to be used, 
the maximum haul distance should not exceed 600 ft.) 

F D = 0.033(distance) 0552 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to the total capital 
cost. This will correct for the addition or reduction of equip- 
ment required to maintain maximum capacity: 

F = 0.888e 10 041l P ercent Kradient)]_ 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life. 

F v = 0.386. 



Track-Type Loader Factor: If track-type loaders are 
used, the factor obtained from the following equation must 
be applied to total capital cost. This factor will account for 
the decrease in production efficiency and the difference in 
equipment cost: 

F T = 0.414(X)0272. 



by 



Total Cost: Front-end loader capital cost is determined 



Y n X F n X F r . X F„ X F. 



T- 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



33 



MINE EQUIPMENT— REAR-DUMP TRUCKS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing the appropriate size and number of diesel 
rear-dump trucks needed to provide the maximum required 
production. Costs do not include transportation, sales tax, 
or discounts. The equation is applied to the following 
variable: 

X =Maximum loose cubic yards of pay gravel, 
overburden, and waste moved hourly by 
rear-dump truck. 

The following capacities were used to calculate the base 
equation: 
3.0-yd 3 

truck 32.3 LCY/h 

5.0-yd 3 

truck 53.4 LCY/h 

6.0-yd 3 

truck 63.6 LCY/h 

8.0-yd 3 

truck 83.5 LCY/h 

10.0-yd 3 

truck 104.2 LCY/h truck 444.8 LCY/h 



12.0-yd 3 

truck 124.5 LCY/h 

16.0-yd 3 

truck 163.9 LCY/h 

22.8-yd 3 

truck 223.5 LCY/h 

34.0-yd 3 

truck 326.3 LCY/h 

47.5-yd 3 



The above capacities are based on the following 
assumptions: 

1. Diesel rear-dump 
trucks. 

2. Loader cycles to fill, 4. 



3. Haul distance, 2,500 ft. 

4. Rolling resistance, 2%, 
nearly level gradient. 



























































































100 000 














































































































10.000 























10 100 1,000 

CRPRCITY, maximum loose cubic yards psr hour 

Mine equipment capital costs - Rsai — dump trucks 



Base Equation: 

Equipment capital cost. . .Y c = 472.09CX) 1 139 

Equipment capital costs consist entirely of the equipment 
purchase price. 

Distance Factor: If the average haul distance is other 
than 2,500 ft, the factor obtained from the following equa- 
tion must be applied to capital cost. This will correct for 
the addition or reduction of equipment required to main- 
tain maximum capacity: 

F D = 0.06240(distance)o 364. 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to total capital cost. 
This will correct for the addition or reduction of equipment 
required to maintain the maximum capacity. (Favorable 
haul gradient should be entered as negative, uphill haul 
grades as positive.) 

Fp = 0.896e'° 056( P ercent gradient)). 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

Frj = 0.243. 

Total Cost: Truck capital cost is determined by 
Y c x F D x F G x F„. 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



34 



CAPITAL COSTS 



MINE EQUIPMENT— SCRAPERS 



Capital Cost Equation: This equation furnishes the cost 
of purchasing the appropriate size and number of scrapers 
needed to provide maximum required production. Costs do 
not include transportation, sales tax, or discounts. The equa- 
tion is applied to the following variable: 

X= Maximum loose cubic yards of pay gravel, over- 
burden, and waste moved hourly by scraper. 

The following capacities were used to calculate the base 
equation: 

330 hp 201 LCY/h 550 hp 420 LCY/h 

450 hp 323 LCY/h 

The above capacities are based on the following 
assumptions: 

1. Standard scrapers. 

2. Rolling resistance, 6%, 
nearly level gradient. 

3. Average haul 
distance, 1,000 ft. 



4. Average operator 
ability. 

5. Dozing distance, 300 
ft. 

6. Efficiency, 50 min/h. 



Base Equation: 

Equipment capital cost 



























































































100 000 
























































































• 






















10,000 






















1 


3 








100 








1 ,0 



CRPHC I T Y t max i mum I oosg cub i c yards pe r hour 



Mine equipment capital costs - Scrapers 



Y c = l,744.42(X)0-934 



Equipment capital costs consist entirely of the equipment 
purchase price. 

Distance Factor: If the haul distance is other than 
1,000 ft, the factor obtained from the following equation 
must be applied to the total capital cost. This will correct 
for the addition or reduction of equipment required to main- 
tain maximum production capacity: 

F D = 0.025 (distance) 0539 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 6%, the factor obtained from 
the following equation must be applied to total capital cost. 
This will correct for the addition or reduction of equipment 
required to maintain the maximum production capacity. 
(Favorable haul gradients are entered as negative, uphill 
haul gradients as positive.) 

F G = 0.776e l0047l P elcenl uradienti]. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F,r = 0.312. 



Total Cost: Scraper capital cost is determined by 
Y c x F D x F G x Fu. 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



35 



PROCESSING EQUIPMENT— CONVEYORS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size con- 
veyors needed to meet maximum required production. A 
separate cost must be calculated for each conveyor in the 
circuit. The cost includes associated drive motors and elec- 
trical hookup. Equipment transportation, sales tax, and dis- 
counts are not accounted for. The equation is applied to the 
following variable: 

X=Maximum cubic yards of material moved hourly 
by conveyor. 

The following capacities were used to calculate the base 
equation: 

18-in-wide 30-in-wide 

conveyor 96 yd 3 /h conveyor 320 yd 3 /h 

24-in-wide 36-in-wide 

conveyor 192 yd 3 /h conveyor 480 yd 3 /h 

Base Equation: 

Equipment capital cost Y c = 4,728.36(X) 0287 

The capital cost consists of 89% equipment purchase price, 
8% installation labor, and 3% construction materials. 

Length Factor: If the required conveyor length is other 
than 40 ft, the factor obtained from the following equation 
must be applied to the calculated capital cost. This factor 
is valid for conveyors 10 to 100 ft long: 
F L = 0.304(length)0-33o. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

Fu = 0.505. 

Total Cost: Conveyor capital cost is determined by 
Y c x F L x F n . 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 























— 


































































100 000 














































































































10.000 























10 100 1.000 

CAPACITY, maximum cubic yards of material moved per hour 

Processing equipment capital costs -Conveyors 



36 



CAPITAL COSTS 



PROCESSING EQUIPMENT— FEED HOPPERS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size 
vibrating feeder needed to meet maximum required produc- 
tion. The cost includes associated drive motors, springs, and 
electrical hookup, plus the expense of a hopper. Equipment 
transportation, sales tax, and discounts are not accounted 
for. The equation is applied to the following variable: 

X = Maximum cubic yards of material handled 
hourly by feed hopper. 

The following capacities were used to calculate the base 
equation: 

12-in-wide unit 16 yd 3 /h 

24-in-wide unit 211 yd 3 /h 

36-in-wide unit 522 yd 3 /h 

The above capacities are based on the following 
assumptions: 

1. Unsized feed. 2. Feed density, 2,300 lb/yd 3 . 

Base Equation: 

Equipment capital cost Y c = 458.48(X) 0470 

The capital cost consists of 82% equipment purchase price, 
14% construction and installation labor, and 4% steel. 



1 


































































m 

L 

a 























T3 

S io.ooo 

o 










































_) 
cr 






















Q_ 

cr 










































i . nnn 























10 100 1,000 

CAPACITY, maximum cubic yards of feed treated per hour 

Processing equipment capital costs - Feed hoppers 



Hopper Factor: In many instances a vibrating feeder 
may not be required. If a hopper is the only equipment 
needed, multiply the calculated cost by the factor obtained 
from the following equation. This factor will account for 
material and labor required to construct and install a 
hopper: 

F H = 0.078ei° 00172<x »i. 

Used Equipment Factor: The factor calculated from 
the following equation accounts for reduced capital expen- 
diture of purchasing equipment having over 10,000 h of 
previous service life: 

F LT = 0.476ei° 00036,X| i. 



Total Cost: Feeder capital cost is determined by 



Y r x F„ x F 



u- 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



37 



PROCESSING EQUIPMENT— JIG CONCENTRATORS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size and 
number of jigs needed to meet maximum required produc- 
tion. The cost includes associated drive motors, piping, and 
electrical hookup. Equipment transportation, sales tax, and 
discounts are not accounted for. The equation is applied to 
the following variable: 

X= Maximum cubic yards of feed handled hourly by 
jig concentrators. 

The following capacities were used to calculate the base 
equation: 

12- by 12-in 36- by 36-in 

simplex 0.617 yd 3 /h triplex . . . 16.659 yd 3 /h 

26- by 26-in 42- by 42-in 

simplex 2.896 ydVh triplex . . .22.675 yd 3 /h 

36- by 36-in 
duplex 11.106 ydVh 

The above capacities are based on the following 
assumptions: 

1. Cleaner service. 4. Slurry density, 40% 

2. Hourly capacity, 0.617 solids. 
yd 3 /ft 2 . 5. Gravity feed. 

3. Feed solids, 3,400 
lb/yd 3 . 

Base Equation: 

Equipment capital cost Y c = 6,403.82(X)°595 

The capital cost consists of 62% equipment purchase price, 
12% construction labor and installation, and 26% construc- 
tion materials. 

Rougher-Coarse Factor: If jigs are to be used for 
rougher service, or a coarse feed, higher productivity will 
be realized. To account for the reduction in equipment re- 
quired to maintain production, the calculated capital cost 
must be multiplied by the following factor: 

F R = 0.531. 

Used Equipment Factor: This factor accounts for the 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

Fu = 0.697. 

Total Cost: Jig concentrator capital cost is determined 

by 

Y c x F R x Fy. 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



































































































10 

l_ 


































XI 

0) 10,000 
o 






























































_1 

IT 
































1- 
































































i .nnn 

































0.1 1.0 10.0 100.0 

CRPRCITY, maximum cubic yards of feed treated per hour 

Processing equipment capital costs - Jig concentrators 



J 



38 



CAPITAL COSTS 



PROCESSING EQUIPMENT— SLUICES 



Capital Cost Equation: This equation furnishes the 
cost of constructing and installing the appropriate size and 
number of sluices needed to meet maximum required pro- 
duction. Costs do not include material transportation or 
sales tax. The equation is applied to the following variable: 

X= Maximum cubic yards of feed handled hourly 
by sluice. 

The following capacities were used to calculate the 
base equation: 

18-in-wide 36-in-wide 

box 20.75 yd 3 /h box 75.00 yd 3 /h 

24-in-wide 42-in-wide 

box 31.25 ydVh box 125.00 yd 3 /h 

30-in-wide 48-in-wide 

box 50.00 yd 3 /h box 218.75 ydVh 

The above capacities are based on the following 
assumptions: 

1. Steel plate 4. Length-to-width ratio, 
construction. 4:1 

2. Angle-iron riffles. 5. Gravity feed. 

3. Feed solids, 3,400 
lb/yd J . 

Base Equation: 
Equipment capital cost Y c = 113.57(X)0 567 

The capital cost consists of 61% construction and installa- 
tion labor, and 39% construction materials. 

Wood Construction Factor: If sluices are to be made 
of wood rather than steel, the following factor will account 
for reduced material and construction costs: 



10,000 



1 ,000 























































































































































































































































































































10 








100 






1 


,0 



CAPACITY, maximum cubic yards of feed treated per hour 



Processing equipment capital costs - Sluices 



F w = 0.499(X) 



-0.023 



Length Factor: This factor will account for changes in 
the desired length of the sluice. The factor obtained from 
the following equation must be applied to capital cost: 

F L = 1.001(L)° 7 53 ; 

where L = desired length divided by length assumed for 
the base calculation (width x 4.0). 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life. 

F v = 0.574. 

Total Cost: Sluice capital cost is determined by 
Y r X F w X F, x F n . 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



39 



PROCESSING EQUIPMENT— SPIRAL CONCENTRATORS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate number 
of spirals needed to meet maximum required production. 
Cost of slurry splitters, fittings, and pipe are all included. 
Costs do not include transportation, sales tax, or discounts. 
The equation is applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by spiral concentrator. 

The following capacities were used to calculate the base 
equation: 

2 starts . 2 yd 3 /h 50 starts 50 yd7h 

10 starts . 10 yd 3 /h 100 starts 100 yd 3 /h 

The above capacities are based on the following 
assumptions: 



1. Rougher service. 

2. Solids per start, 
1.75 st/h. 

3. Feed solids, 
3,400 lb/yd 3 . 




4. Slurry density, 
10% solids. 

5. Gravity feed. 


Base Equation: 






Equipment capital 


cost. 


. . Y c = 3,357.70(X) 0999 



The capital cost consists of 71% equipment purchase price, 
13% construction labor and installation, and 16% construc- 
tion materials. 

Cleaner-Scavenger Service Factor: If spirals are to 
be used for cleaner or scavenger functions, unit capacity 
will decrease. To account for additional equipment needed 
to maintain production, calculated capital cost must be 
multiplied by the following factor: 

F c = 2.333. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F v = 0.654. 



1 ,000,000 



































































































0) 

k 100,000 






























































































"□ 
































o 

u 
































_i 
<r 

Jl 10,000 































































































































































































I 10 100 1,000 

CAPACITY, maximum cubic yards of feed treated per hour 

Processing equipment capital costs - Spiral concentrators 



Total Cost: Spiral concentrator capital cost is deter- 
mined by 



Y c * F c x F„. 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



40 



CAPITAL COSTS 



PROCESSING EQUIPMENT— TABLE CONCENTRATORS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size and 
number of tables needed to meet maximum required pro- 
duction. Cost includes associated drive motors, piping, and 
electrical hookup. Equipment transportation, sales tax, and 
discounts are not accounted for. The equation is applied to 
the following variable: 

X = Maximum cubic yards of feed handled hourly 
by table concentrator. 

The following capacities were used to calculate the base 
equation: 

18 ft 2 0.147 ydVh 140 ft 2 1.471 yd7h 

32 ft 2 0.442 yd 3 /h 240 ft 2 2.471 yd7h 

80 ft 2 0.882 yd 3 /h 

The above capacities are based on the following 
assumptions. 



1. Cleaner service. 

2. Feed solids, 3,400 

lb/yd 3 . 



3. Slurry density, 
25% solids. 

4. Gravity feed. 



Base Equation: 

Equipment capital cost. . . Y c 



20,598.06(X)° 



The capital cost consists of 62^ equipment purchase price, 
12^ construction labor and installation, and 26% construc- 
tion materials. 

Rougher-Coarse Factor: If tables are to be used for 
rougher service, or a coarse feed, higher productivity will 
be realized. To account for reduction in equipment required 
to maintain production, the calculated capital cost must be 
multiplied by the following factor: 

F K = 0.568. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F, = 0.596. 
































































































10 

O 100,000 






























































































"O 
































n 
a 
u 
































_j 

r 

^ 10,000 






























































u 
































































































1 .000 

































0.1 1.0 10.0 100.0 

CRPACITY, maximum cubic yards of feed treated per hour 

Processing equipment capital costs - Table concentrators 



Total Cost: Table concentrator capital cost is deter- 
mined by 



Y, >< F R x F L „ 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



41 



PROCESSING EQUIPMENT— TROMMELS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size trom- 
mels needed to meet maximum required production. Cost 
includes associated drive motors, piping, and electrical 
hookup. Equipment transportation, sales tax, and discounts 
are not accounted for. The equation is applied to the follow- 
ing variable: 

X = Maximum cubic yards of feed handled hourly 
by trommels. 

The following capacities were used to calculate the base 
equation: 

3.0-ft diam 
3.5-ft diam 
4.0-ft diam 
4.5-ft diam 



40 yd 3 /h. 5.0-ft diam 

50 ydVh. 5.5-ft diam 

85 yd 3 /h. 7.0-ft diam 
150 yd 3 /h. 



. 250 yd 3 /h. 
. 300 yd 3 /h. 
. 500 yd 3 /h. 



The above capacities are based on the following 
assumptions: 



1. Trommels are sec- 
tioned for scrubbing 
and sizing. 



2. Gravity feed. 

3. Feed density, 2,300 
lb/yd 3 . 



00,000 





- 














- 












^s , 




- 






































































































10.000 





















10 100 1,000 

CRPRCITY, max i mum cubic yards of feed treated per hour 

Processing equipment capital costs - Trommels 



Base Equation: 

Equipment capital cost. 



7,176.21(X) 0559 



The capital cost consists of 64% equipment purchase price, 
26% construction and installation labor, and 10% construc- 
tion materials. 

Used Equipment Factor: This factor accounts for the 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F L . = 0.516. 
Total Cost: Trommel capital cost is determined by 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



42 



CAPITAL COSTS 



PROCESSING EQUIPMENT— VIBRATING SCREENS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size and 
number ol' vibrating screens needed to meet maximum re- 
quired production. Cost includes installation and electrical 
hookup of both the screens and the associated drive motors. 
Equipment transportation, sales tax, and discounts have 
not been taken into account. The equation is applied to the 
following variable: 

X = Maximum cubic yards of feed handled hourly 
by vibrating screens. 

The following capacities were used to calculate the base 
equation: 

30-ft 2 screen 96-ft 2 screen 

surface 47 yd : 7h surface 150 yd 3 /h 

56-ft 2 screen 140-ft 2 screen 

surface 87 ydVh surface 218 yd 3 /h 

60-ft 2 screen 

surface 93 yd 3 /h 

The above capacities are based on the following 
assumptions: 

1. An average of 0.624 ft 2 2. Feed solids, 
of screen is required for 3,120 lb/yd 3 , 

every cubic yard of 3. Gravity feed, 
hourly capacity. 

Base Equation: 

Equipment capital cost. . . Y ( . = 1,870. 20(X) 06:!1 

The capital cost consists of 75% equipment purchase price, 
I0 r /r construction and installation labor, and 15% construc- 
tion materials. 



I ,000,000 



£ 100.000 



10,000 



• 



10 100 1,000 

CRPflCITY, maximum cubic yards of feQd treated per hour 

Processing equipment capital costs - Vibrating screens 



Capacity Factor: If anticipated screen capacity is other 
than 0.624 ft 2 /yd 3 of hourly feed capacity, the calculated 
capital cost must be multiplied by the following factor. This 
will account for the increase or reduction in equipment size 
required to maintain production: 

F ( . = 1.322(C) 0629 , 

where C = anticipated capacity in square feet per cubic yard 
of hourly feed. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F l} = 0.565. 



by 



Total Cost: Vibrating screen capital cost is determined 



Y ( . x F c x F LI . 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



43 



SUPPLEMENTAL— BUILDINGS 



Capital Cost Equation: This equation provides the cost 
of materials and construction for any buildings needed at 
the site. These may include storage sheds, shops, or mill 
buildings. Costs do not include sales tax, material transpor- 
tation, or discounts. A separate cost must be calculated for 
each building, and the equation is applied to the following 
variable: 

X = Estimated floor area, in square feet. 

Building costs are based on the following assumptions: 



I 00 . 000 



1. Average quality tem- 
porary structures. 

2. Steel frame with 
metal siding and 
roofing. 



3. Concrete perimeter 
foundations with wood 
floors. 

4. Electricity and 
lighting provided. 



Base Equation: 

Capital cost Y c = 34.09(X) a907 

The capital cost consists of 34% construction labor, 41% con- 
struction materials, and 25% equipment. 

Cement Floor Factor: If a cement floor is required, 
the cost calculated from the base equation must be 
multiplied by the factor obtained from the following 
equation: 

F c = 1.035(X) 0008 . 

Plumbing Factor: If plumbing is required, the follow- 
ing factor must be applied to the total capital cost: 

F p = 1.013(X) 0002 . 

Foundation Factor: If a concrete foundation and wood 
floor are not needed, multiply the capital cost by the factor 
obtained from the following equation. This will account for 
the cost of wood blocks and sills for the foundation: 

F F = 0.640(X) 0026 . 
Total Cost: Building capital cost is determined by 



10,000 




,000 
FLOOR RRER, square feet 

Supplemental capital costs - Buildings 



Y„ x F„ x F„ x F„ 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



44 



CAPITAL COSTS 



SUPPLEMENTAL— EMPLOYEE HOUSING 



Capital Cost Equation: Costs of purchasing, outfitting, 
and installing trailers for workers living at the minesite 
are provided by this equation. Costs are based on fair qual- 
ity single-wide trailers capable of meeting minimum 
building code requirements. Costs do not include sales tax, 
equipment transportation, or discounts. The equation is ap- 
plied to the following variable: 

X = Average loose cubic yards of overburden and 
pay gravel handled hourly. 

The following capacities were used to calculate the base 
equation: 

25 LCY/h . . 3.1 workers 150 LCY/h . 6.6 workers 
50 LCY/h . . 4.2 workers 400 LCY/h . 9.9 workers 

The above capacities are based on the following 
assumptions: 

1. Average workforce for 2. Two workers per 
placer mines in the trailer, 

western United States 3. Trailers contain cook- 
( including Alaska). ing facilities. 

Base Equation: 

Capital cost Y c = 7,002.51(X) - 418 

The capital cost consists of 90% equipment purchase price, 
T7c construction and installation labor, and 3% construc- 
tion materials. 



10,000 




100 1,000 

CAPACITY, avGrogg Ioqsg cubic yards pay 
gravel plus overburden mined per hour 

Supplemental capital costs - Employee housing 



Used Equipment Factor: This factor accounts for the 
reduced expense of purchasing used trailers. The adjusted 
cost is obtained by multiplying the calculated capital cost 
by the following factor: 



F LI = 0.631. 



Workforce Factor: The equation used to compute labor 
for capital cost estimation is: 



Workforce = 0.822(X)' 



0.415 



If the workforce for the operation under evaluation is 
known, and is different than that calculated from the above 
equation, the correct capital cost may be obtained from the 
following equation: 

Y r = (Number of workers) x 8,608.18. 



Total Cost: Employee housing capital cost is deter- 
mined by 

Y c * F . 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



45 



SUPPLEMENTAL— GENERATORS 



Capital Cost Equation: This equation provides the cost 
of puixhasing and installing the appropriate size generator 
required to meet maximum production. Cost includes in- 
stallation and connection through the fuse box, and allows 
for mill, mine, camp, and ancillary function power consump- 
tion. Costs do not include equipment transportation, sales, 
tax, or discounts. The equation is applied to the following 
variable: 

X = Maximum cubic yards of feed handled per 

hour. 

The following capacities were used to calculate the base 
equation: 

10-kVV 75-kW 

generator ... 10 yd 3 /h generator . . . 125 yd 3 /h 
30-kW 125-kW 

generator ... 40 yd 3 /h generator . . . 200 yd 3 /h 
45-kW 250-kW 

generator ... 75 yd 3 /h generator . . . 400 yd 3 /h 

The above capacities are based on the assumption that 
0.57 kW is needed for every cubic yard of mill capacity. This 
is average for a mine with a basic plant containing trom- 
mels, conveyors, mechanical gravity separation devices (jigs 
or tables), and other necessary ancillary equipment. In all 
cases, a slightly higher rated generator has been selected 
for costing purposes to account for demand surges and 
miscellaneous electrical consumption, such as camp elec- 
tricity. A factor is provided below for operations with power 
consumption rates other than 0.57 kW/yd 3 . 



10,000 



,000 




1 ,000 



10 100 

MILL CflPRCITY, maximum cubic yards of feed treated per hour 

Supplemental capital costs - Generators 



Base Equation: 

Equipment capital cost. 



1,382.65(X) - 604 



The capital cost consists of 75% equipment purchase price, 
19% construction and installation labor, and 6% construc- 
tion materials. 

Alternate Power Consumption Factor: If anticipated 
power consumption rate is other than 0.57 kW/yd 3 mill 
capacity, the capital cost must be multiplied by the factor 
obtained from the following equation: 

F p = 1.365(P) 061g , 

where P = anticipated power consumption rate. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 

F v = 0.481. 
Total Cost: Generator capital cost is determined by 



Y, 



F D xF, 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



Ui 



CAPITAL COSTS 



SUPPLEMENTAL— PUMPS 



Capital Cost Equation: This equation furnishes the 
cost of purchasing and installing the appropriate size of 
pump needed for each particular function (i.e., providing 
Irish mill water, recirculating spent water through settling 
ponds, etc.). If more than one pump is required, a separate 
cost must be calculated for each installation. Guidelines for 
pump requirements are listed in section 1. In general, 
however, at least one pump will be required if water is 
recycled through settling ponds. Costs of diesel-driven cen- 
trifugal pumps, polyvinyl chloride (PVC) pipe, and pump 
and pipe installation labor are all considered. Costs of equip- 
ment transportation, sales tax, and discounts are not in- 
cluded. The equation is applied to the following variable: 

X = Maximum gallons per minute of water 
handled. 

The following capacities were used to calculate the base 



equation: 

0.50-hp 
pump . 

2.00-hp 
pump . 

5.25-hp 
pump . 



50 gpm 
200 gpm 
500 gpm 



10.50-hp 
pump . . 

18.50-hp 
pump . . 

37.00-hp 
pump . . 



1,000 gpm 
1,750 gpm 
3,500 gpm 



10,000 
































































































0! 

L 


































o 

ui 1 ,000 
a 






























































_i 
a: 
































Q_ 

cr 
































































100 
1 
































D 








100 






1 


,000 






10, c 



PUMP CAPACITY, maximum gal Ions per minute 



Supplemental capital casts - Pumps 



The above capacities are based on the following 



assumptions: 

1. Total head of 25 ft. 

2. Diesel-powered pumps. 



Abrasion-resistant 
steel construction. 
Total engine-pump ef- 
ficiency of 60%. 



Base Equation: 

Equipment capital cost. 



63.909(X) 0618 



The capital cost consists of 70% equipment purchase price, 
22 r/ f construction materials, and 8% construction and in- 
stallation labor. 

Head Factor: If total pumping head is other than 
25 ft, the factor calculated from the following equation will 
correct for changes in pump size requirements. The product 
of this factor and the original cost will provide the ap- 
propriate figure: 

F H = 0. 125(H) 6:i? , 

where H = total pumping head. 

Used Equipment Factor: This factor accounts for 
reduced capital expenditure of purchasing equipment hav- 
ing over 10,000 h of previous service life: 



F v = 0.615. 



Total Cost: Pump capital cost is determined by 



Y c * F H x Fu . 



This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



CAPITAL COSTS 



47 



SUPPLEMENTAL— SETTLING PONDS 



Capital Cost Equation: This equation furnishes the 
cost of settling ponds for waste-water treatment. Costs of 
labor and equipment operation for site selection, size deter- 
mination, rough surveying, excavation, ditching, grading, 
and placement of sized gravel are all included. The equa- 
tion is applied to the following variable: 

X = Maximum mill water consumption, in gallons 
per minute. 

If the water consumption rate is not known, one can be 
estimated from the following equation: 

X = 94.089(Y) 0546 , 

where Y = maximum cubic yards of mill feed handled per 
hour. 

The following capacities were used to calculate the base 
equation: 

400 gpm 1,426-yd 3 900 gpm 



600 gpm 



1,426-yd 3 

liquid 

capacity. 
2,139-yd 3 

liquid 

capacity 



1,400 gpm 



3,208-yd 3 

liquid 

capacity 
4,991-yd 3 

liquid 

capacity 



The above capacities are based on the following 
assumptions: 



1. Pond located in mined- 
out area. 

2. Excavated by 
bulldozer. 



3. Capable of holding 
12 h of waste water 
produced by mill. 

4. Based on jig plant 
water consumption 
rate. 



10,000 
































































































































1 000 
































































































































































100 






























































































































































in 




























1 



10 100 1,000 10,000 

MILL WRTER CONSUMPTION, maximum gallons per minute 

Supplemental capital costs - Sett I i ng ponds 



Base Equation: 

Capital cost. . . Y c 



3.982(X) ' 952 



The capital cost consists of 75% construction labor, 13% fuel 
and lubrication, and 12% equipment parts. 

Liner Factor: In order to meet water quality standards, 
some settling ponds must be lined with an impervious 
material. If such a liner is required, total capital cost must 
be multiplied by the factor calculated from the following 
equation: This factor covers cost of the liner and associated 
installation labor: 

F L = 27.968(X)-°- 314 . 

Total Cost: Settling pond capital cost is determined by 

Y c >< F L . 

This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 5 for final capital cost 
calculation. 



48 



OPERATING COSTS 



OVERBURDEN REMOVAL— BULLDOZERS 



Operating Cost Equations: These equations provide 
the cost of excavating and relocating overburden using 
bulldozers. Costs are reported in dollars per loose cubic yard 
of overburden handled. The equations are applied to the 

till lowing variable: 

X Maximum loose cubic yards of pay gravel, 
overburden, and tails moved hourly by 
bulldozer. 

The base equations assume the following: 



I .000 



1. No ripping. 

2. Cutting distance, 
50 ft. 

3. Efficiency, 50 min/h. 



Base Equations: 



4. Dozing distance, 
300 ft. 

5. Average operator 
ability. 

6. Nearly level gradient. 



Equipment operating cost. 
Labor operating cost 



Y K = 0.993(Xr - 430 
Y,' = 14.0KX)- 0945 



Equipment operating costs average 47% parts and 53% fuel 
and lubrication. Labor operating costs average 86% oper- 
ator labor and 14% repair labor. 



oi 0.100 
a 

o 



O.OIO 







































































































































^^ Equipment 




































Labor 

























10 I 00 1 , 000 

CAPACITY, maximum loose cubic yards per hour 

Overburden removal operating costs - Bulldozers 



Distance Factor: If the average dozing distance is other 
than 300 ft, the factor obtained from the following equa- 
tion must be applied to total cost per loose cubic yard: 



F„ = 0.00581(distance) a904 . 



Gradient Factor: If the average gradient is other than 
level, the factor obtained from the following equation must 
be appled to the total cost per loose cubic yard: 



1.041e" 



fill Ki-iulivnli) 



Ripping Factor: If ripping is required, total operating 
cost must be multiplied by the following factor. This will 
account for the reduced productivity associated with ripping: 

F K = 1.595. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 



Equipment factor U, 

Labor factor U, 



1.206(X)-°- 013 
0.967(X) 0015 



Digging Difficulty Factor: Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required. 
If so, one of the following should be applied to total cost per 
loose cubic yard: 

F H , easy digging . 0.830 F H , medium-hard 



F„, medium 



digging 1.250 



digging 1.000 F H , hard digging . 1.670 



Total Cost: Cost per loose cubic yard of overburden is 

determined by 

[Y E (U ) + Y L (U,)] x F D x F G x F H x F R . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden handled by 
bulldozer. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



49 



OVERBURDEN REMOVAL— DRAGLINES 



Operating Cost Equations: These equations provide 
the cost of excavating overburden using draglines. Costs 
are reported in dollars per loose cubic yard of overburden 
handled. The equations are applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by dragline. 

The base curves assume the following: 

1. Bucket efficiency, 3. Swing angle, 90°. 
0.90. 4. Average operator 

2. Full hoist. ability. 

Base Equations: 

Equipment operating cost. . . Y E =1.984(X)-° 390 
Labor operating cost Y L =12.19(X)-°-8«> 

Equipment operating costs consist of 67% parts and 33% 
fuel and lubrication. Labor operating costs consist of 78%- 
operator labor and 22% repair labor. 

Swing Angle Factor: If average swing angle is other 
than 90°, the factor obtained from the following equation 
must be applied to the total cost per loose cubic yard: 

F s =0.304(swing angle) 0269 . 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 











































































— Equipment 
























































N Lc±Jor 



































































10 100 1,000 

CRPHCITY , max i mum I oose cub i c yards per hour 

Overburden removal operating costs - Draglines 



Equipment factor U e = 1.162(X)-«oi7 

Labor factor . . .'. U, = 0.989(X)oooe 

Total Cost: Cost per loose cubic yard of overburden 
is determined by 

[Y E (U e ) + Y L (U,)] x F s . 



The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden handled by 
dragline. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



;>o 



OPERATING COSTS 



OVERBURDEN REMOVAL— FRONT-END LOADERS 



Operating Cost Equations: These equations provide 
t he cost of relocating overburden using wheel-type front- 
end loaders. Costs are reported in dollars per loose cubic 
yard of overburden handled. The equations are applied to 
the following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by front-end 
loader. 

The base equations assume the following: 

1. Haul distance, 500 ft. 3. Inconsistent operation. 

2. Rolling resistance, 2%, 4. Wheel-type loader 
nearly level gradient. 

Base Equations: 

Equipment operating cost. . . Y R = 0.407(X)" 225 
Labor operating cost Y, =13.07(X)-°^e 

Equipment operating costs average 22% parts, 46% fuel and 
lubrication, and 32%- tires. Labor operating costs average 
909; operator labor and 10% repair labor. 

Distance Factor: If average haul distance is other than 
500 ft, the factor obtained from the following equation must 
be applied to the total cost per loose cubic yard: 

F 1) =0.023(distance)" 61fi . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to the total cost per 
loose cubic yard: 

F r = 0.877e |lu)46l P L ' ra ' nt K'«dientl| 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 



I .000 



(0 0. 





100 

































































































Equipment 


























































Lcbor 















































10 100 1,000 

CflPRCITY, maximum I aoss cubic yards per hour 

Overburden removal operating costs - Front-end loaders 



Equipment factor U e = 1.162(X)-°-°" 

Labor factor U, = 0.989(X)°.ooe 



Track-Type Loader Factor: If track-type loaders are 
used, the following factors must be applied to the total cost 
obtained from the base equations: 

Equipment factor T e = 1.378 

Labor factor T, = 1.073 

Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U e XT e ) + Y L (U,XT,)] x F D x F G . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden handled by 
dragline. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



51 



OVERBURDEN REMOVAL— REAR-DUMP TRUCKS 



Operating Cost Equations: These equations provide 
the cost of hauling overburden using rear-dump trucks. 
Costs are reported in dollars per loose cubic yard of over- 
burden handled. The equations are applied to the follow- 
ing variable: 

X=Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by rear dump 
truck. 

The base equations assume the following: 



4. Average operator 
ability. 

5. Nearly level gradient. 



1. Haul distance, 
2,500 ft. 

2. Loader cycles to 
fill, 4. 

3. Efficiency, 50 min/h. 

Base Equations: 

Equipment operating cost . . . Y E =0.602(X)-° 296 
Labor operating cost Y L =11.34(XH- 891 

Equipment operating costs consist of 28% parts, 58% fuel 
and lubrication, and 14% tires. Labor operating costs con- 
sist of 82% operator labor and 18% repair labor. 

Distance Factor: If average haul distance is other than 
2,500 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F D =0.093(distance) 0311 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F<- = 0.907e' 0049l P e, ' cent gradient)] 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 

Equipment factor U e =0.984(X)-°° 16 

Labor factor U,=0.943(X)o°2i 

Total Cost: Cost per loose cubic yard of overburden is 
determined by 



0. 100 



0.010 





















































































































^-Eq 


jipment 




































\ Labor 













































10 1 00 I , 000 

CflPRCITY, maximum loose cubic yards per hour 

Overburden removal operating costs - Rear-dump trucks 



[Y E (U e +Y L (U,)] x F D x F 



G- 



The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden handled by truck. 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 6 for final operating cost 
calculation. 



52 



OPERATING COSTS 



OVERBURDEN REMOVAL— SCRAPERS 



Operating Cost Equations: These equations provide 
the cost of excavating and hauling overburden using 
scrapers. Costs are reported in dollars per loose cubic yard 
of overburden handled. The equations are applied to the 
following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by scraper. 

The base curves assume the following: 



1. Standard scrapers. 

2. Rolling resistance, 
6V( , nearly level 
gradient. 

3. Efficiency, 50 min/h. 



4. Haul distance, 1,000 ft. 

5. Average operator 
ability. 



Base Equations: 

Equipment operating cost. . . Y F =0.325(X)-°- 21() 
Labor operating cost Y, =12.01(X)- 0f »° 

Equipment operating costs consist of 48% fuel and lubrica- 
tion, 347f tires, and 18% parts. Labor operating costs con- 
sist of 88/? operator labor and 12% repair labor. 

Distance Factor: If average haul distance is other than 
1,000 ft, the factor obtained from the following equation 
must be applied to the total cost per loose cubic yard: 
F|,=0.01947(distance) or ' 77 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 6%, the factor obtained from 
the following equation must be applied to the total cost per 
loose cubic yard: 

F (; = 0.776e |no47l P l ' ra ' ,u KnidiontH. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 

Equipment factor U e =1.096(X)-°-°°e 

Labor factor U. = 0.845(X)°-°*» 



a 
oi 0. 





















































































































■ Equipment 
























































^ Labor 

























ID 100 1,000 

CRPFCITY, maximum loose cubic yards par hour 

Overburden removal operating costs - Scrapers 



Total Cost: Cost per loose cubic yard of overburden is 
determined by 

[Y E (U,) + Y L (U,)] x F D x F G . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden handled by 
scraper. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



53 



MINING— BACKHOES 



Operating Cost Equations: These equations provide 
the cost of excavating pay gravel using backhoes. Costs are 
reported in dollars per loose cubic yard of pay gravel han- 
dled. The equations are applied to the following variable: 

X= Maximum loose cubic yards of pay gravel moved 
hourly by backhoe. 

The base equations assume the following: 

1. Easy digging 4. Average operator 
difficulty. ability. 

2. Swing angle, 60° to 5. No obstructions 
90°. (boulders, tree roots, 

3. Up to 50% of etc.). 
maximum digging 

depth. 

Base Equations: 

95-200 LCY/h: 

Equipment operating cost . . .Y E =8.360(X)- 1019 
Labor operating cost Y L =-17.53(XH-«» 

175-275 LCY/h: 

Equipment operating cost . . .Y E =11,44(X)- 1021 
Labor operating cost Y L =17.25(XH-°°° 

250-375 LCY/h: 

Equipment operating cost . . .Y E =15.17(X)- 1003 
Labor operating cost Y L =19.97(X)-! ° 17 

350^75 LCY/h: 

Equipment operating cost . . .Y E =22.59(Xh 0995 
Labor operating cost Y L =16.55(X)-°9" 

Equipment operating costs consist of 38% parts and 62% 
fuel and lubrication. Labor operating costs consist of 88%' 
operator labor and 12% repair labor. 

Digging Depth Factor: If average digging depth is 
other than 50% of maximum, the factor obtained from the 
following equation must be applied to the total cost per loose 
cubic yard of pay gravel: 

F D =0.09194(percent of maximum digging depth) 0608 . 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 

Equipment factor U e =1.078(X)-° 003 

Labor factor U, = 0.918(X)0-02i 

Digging Difficulty Factor: Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required. 



io 0.100 



0.010 























































- 


























\ 
\ 
\ 

\ 




















\ 






















X \ 


















\ \ 


\^> 


















N 





























100 1,000 

CRPRCITY, maximum loose cubic yards per hour 

Equipment Labor 

Mining operating costs - Backhoes 



If so, one of the following should be applied to total cost per 
loose cubic yard of pay gravel: 

F H , easy digging . . . 1.000 F H , medium-hard 

F H , medium digging 1.500 

digging 1.250 F H , hard digging 1.886 

Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y e (U e ) + Y L (U,)] x F D x F H . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of pay gravel handled by 
backhoe. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



.V! 



OPERATING COSTS 



MINING— BULLDOZERS 



Operating Cost Equations: These equations provide 
the cost of excavating and relocating pay gravel using 
bulldozers. Costs are reported in dollars per loose cubic yard 
of pay gravel handled. The equations are applied to the 
following variable: 

X=Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by bulldozer. 

The base equations assume the following: 



1. No ripping. 

2. Cutting distance, 50 
ft. 

3. Efficiency, 50 min/h. 



4. Dozing distance, 300 
ft. 

5. Average operator 
ability. 

6. Nearly level gradient. 



Base Equations: 

Equipment operating cost. 



Y F =0.993(X)-0430 



Labor operating cost Y L =14.01(X)-° 945 

Equipment operating costs average 47% parts and 53% fuel 
and lubrication. Labor operating costs average 86% operator 
labor and 14% repair labor. 

Distance Factor: If average dozing distance is other 
than 300 ft, the factor obtained from the following equa- 
tion must be applied to the total cost per loose cubic yard: 

F.^O.OOSSKdistance) 0904 . 



0.010 









































































































































^•^ Equ i omen t 




































N Labor 

























100 1,000 

CRPflCITY, maximum I qqsq cubic yards per hour 

Mining operating costs - Bulldozers 



Gradient Factor: If average gradient is other than 
level, the factor obtained from the following equation must 
be applied to the total cost per loose cubic yard: 

F . = 1 041e |0015, P e,cent gradient)] 

Ripping Factor: If ripping is required, total operating 
cost must be multiplied by the following factor. This will 
account for reduced productivity associated with ripping: 

F R = 1.595. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 

Equipment factor U e =1.206(X)-ooi3 

Labor factor U, = 0.967(X)°-°i5 

Digging Difficulty Factor: Parameters given in the 
discussion on site adjustment factors in section 1 should be 
used to determine if a digging difficulty factor is required 
If so, one of the following should be applied to total cost per 
loose cubic yard. 

F H , easy digging . . . 0.830 F H , medium-hard 

F H , medium digging 1.000 digging 1.250 

F H , hard digging 1.670 



Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y E (U e )+Y L (U,)]xF D xF G xF H xF R . 

The total cost per loose cubic yard must then be multiplied 
by total yearly amount of pay gravel handled by bulldozer. 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 6 for final operating cost 
calculation. 



OPERATING COSTS 



55 



MINING— DRAGLINES 



Operating Cost Equations: These equations provide 
the cost of excavating pay gravel using draglines. Costs are 
reported in dollars per loose cubic yard of pay gravel han- 
dled. The equations are applied to the following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by dragline. 

The base curves assume the following: 



1. Bucket efficiency, 
0.90. 

2. Full hoist 



3. Swing angle, 90°. 

4. Average operator 
ability. 



Base Equations: 

Equipment operating cost. . . Y E = 
Labor operating cost Y L = 



T.984(X)-°-390 

12.19(XH-888 



Equipment operating costs consist of 67% parts and 33% 
fuel and lubrication. Labor operating costs consist of 78% 
operator labor and 22% repair labor. 

Swing Angle Factor: If the average swing angle is 
other than 90°, the factor obtained from the following equa- 
tion must be applied to total cost per loose cubic yard: 

F s =0.304(swing angle) 0269 . 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by the factors obtained from the following 
equations: 

Equipment factor U e =1.162(X)-° 017 

Labor factor U| = 0.989(X) 0006 

Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y lJ CU e )+Y L (U I )]xF s . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of pay gravel handled by 
dragline. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



0) 0. 
a 











































































^*^ Equ i pmen t 
























































^ Lcbor 



































































10 100 1,000 

CRPRCITY, maximum loose cubic yards pGr hour 

Mining operating costs - Draglines 



56 



OPERATING COSTS 



MINING— FRONT-END LOADERS 



Operating Cost Equations: These equations provide 
the cost of hauling pay gravel using wheel-type front-end 
loaders. Costs are reported in dollars per loose cubic yards 
of pay gravel handled. The equations are applied to the 
following variable: 

X=Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by front-end 
loaders. 

The base equations assume the following: 

1. Haul distance, 500 ft. 3. Inconsistent operation. 

2. Rolling resistance, 2%, 4. Wheel-type loader, 
aearly level gradient. 

Base Equations: 

Equipment operating costs . . Y E = 0.407(X)-°225 
Labor operating costs Y L = 13.07(X)-0936 

Equipment operating costs average 22% parts, 46% fuel and 
lubrication, and 32% tires. Labor operating costs average 
90% operator labor and 10% repair labor. 

Distance Factor: If the average haul distance is other 
than 500 ft, the factor obtained from the following equa- 
tion must be applied to total cost per loose cubic yard: 

F D = 0.023(distance) 0616 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to the total cost per 
loose cubic yard: 

F r = 0.877e l0046( P elcent Kradient)|_ 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e = 1.162(Xr 0017 

Labor factor II = 0.989(X)° 006 



I .000 



0.100 



0.010 

































































































Equ 1 pmen t 


























































Lcbor 















































100 1,000 

CAPACITY, maximum I oosq cubic yards per hour 

Mining operating costs - Front-end loaders 



Track-Type Loader Factor: If track-type loaders are 
used, the following factors must be applied to total cost ob- 
tained from the base equations: 

Equipment factor T e = 1.378 

Labor factor T, = 1.073 

Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y E (U e XT e )+ ■ Y L (U,XT,)]x F D x F G . 

The total cost per loose cubic yard must then be multiplied 
by total yearly amount of pay gravel handled by front-end 
loader. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



57 



MINING— REAR-DUMP TRUCKS 



Operating Cost Equations: These equations provide 
the cost of hauling pay gravel using rear-dump trucks. Costs 
are reported in dollars per loose cubic yard of pay gravel. 
The equations are applied to the following variable: 

X= Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by rear dump 
truck. 

The base equations assume the following: 



1. Haul distance, 2,500 
ft. 

2. Loader cycles to fill, 4. 

3. Efficiency, 50 min/h. 

Base Equations: 

Equipment operating cost. 



4. Average operator 
ability. 

5. Rolling resistance, 2%, 
nearly level gradient. 



Y F =0.602(X)-0 296 



Labor operating cost Y L =11.34(XH>89i 

Equipment operating costs consist of 28% parts, 58% fuel 
and lubrication, and 14% tires. Labor operating costs con- 
sist of 82% operator labor and 18% repair labor. 

Distance Factor: If average haul distance is other than 
2,500 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F D =0.093(distance) 0:J11 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F =0.907e IOO49l P ercent tn" adient) l. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service'life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e =0.984(X) 0016 

Labor factor U,=0.943(X)0 02i 

Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y E (U c )+Y L (U,)]xF D xF G . 





















































































































^~" Equ i pmen t 




































\ Labor 













































10 100 1,000 

CAPACITY, maximum loose cubic yards per hour 

Mining operating costs - Rear-dump trucks 



The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of pay gravel handled by rear- 
dump truck. This product is subsequently entered in the 
appropriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



58 



OPERATING COSTS 



MINING— SCRAPERS 



Operating Cost Equations: These equations provide 
the cost of excavating and hauling pay gravel using 
scrapers. Costs are reported in dollars per loose cubic yard 
of pay gravel handled. The equations are applied to the 
following variables: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by scraper. 

The base equations assume the following: 

1. Standard scrapers. 4. Haul distance, 1,000 



I .000 



2. Rolling resistance, 6%, 
nearly level gradient. 

3. Efficiency, 50 min/h. 



ft. 

Average operator 

ability. 



Base Equations: 

Equipment operating cost. . . Y E =0.325(X) 0210 
Labor operating cost Y L '=12.01(X)-°- 930 

Equipment operating costs consist of 48% fuel and lubrica- 
tion, 34% tires, and 18% parts. Labor operating costs con- 
sist of 88^ operator labor and 12% repair labor. 

Distance Factor: If average haul distance is other than 
1,000 ft, the factor obtained from the following equation 
must be applied to the total cost per loose cubic yard: 

F„=0.01947(distance) " 7 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 6%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F r = 0.776e IOO47, P t ' m -' nt Kradientll, 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e =1.096(X)-°-°° 6 

Labor factor U, = 0.845(X)°°34 



0) 0.100 





















































































































— Equipment 
























































^ Labor 

























10 100 ! ,000 

CRPflCITY, maximum I qqsq cubic yards per hour 

Mining operating costs - Scrapers 



Total Cost: Cost per loose cubic yard of pay gravel is 
determined by 

[Y E (U e )+Y L (U,)]xF D xF G . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of pay gravel handled by scraper. 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 6 for final operating cost 
calculation. 



OPERATING COSTS 



59 



PROCESSING— CONVEYORS 



Operating Cost Equations: These equations provide 
the cost of moving gravel using conveyors. Costs are 
reported in dollars per cubic yard of gravel handled and in- 
clude the operating cost of the conveyor along with the 
drive. The equations are applied to the following variable: 

X = Maximum cubic yards of material moved 
hourly by conveyor. 

The base equations assume the following: 

1. Conveyors, 40 ft long. 3. Nearly level setup. 

2. Feed, 3,120 lb/yd 3 . 

Base Equations: 

Equipment operating cost. . .Y E = 0.218(X)-°- 561 
Labor operating cost Y L = 0.250(X)" 702 

Equipment operating costs average 72% parts, 24% elec- 
tricity, and 4% lubrication. Labor operating costs consist 
entirely of repair labor. 

Conveyor Length Factor: If conveyor length is other 
than 40 ft, factors obtained from the following equations 
must be applied to respective portions of the operating costs. 
These factors are valid for conveyors 10 to 100 ft long: 

Equipment factor L e = 0.209(length) 0431 

Labor factor L, = 0.245(length)° 39 ° 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by the following factors: 

Equipment factor U e = 1.155 

Labor factor .U, = 1.250 



3 

u 0.0101- 



E 0.001 



1 












I 












































^\ 


















































"V. 




















^^ Equipment 




















! 
















^ Labor 


I 
1 

! 























10 100 1,000 

CAPACITY, maximum cubic yards of material moved per hour 

Processing operating costs - Conveyors 



Total Cost: 

mined by 



Cost per cubic yard of gravel is deter- 



[Y E (L e XU e ) + Y L (L,XU,)]. 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of feed handled by conveyor. (A 
separate operating and total yearly cost must be calculated 
for each conveyor in the circuit.) This product is subsequent- 
ly entered in the appropriate row of the tabulation shown 
in figure 6 for final operating cost calculation. 



till 



OPERATING COSTS 



PROCESSING— FEED HOPPERS 



Operating Cost Equations: These equations provide 
cost of material transfer using vibrating feeders. Costs are 
reported in dollars per cubic yard of feed and include the 
operating cost of the hopper, feeder, and drive motor. The 
equations are applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by feed hopper. 

The base equations assume the following: 

I. Unsized feed. 2. Feed solids, 2,300 

lb/yd 3 . 



Base Equations: 

Equipment operating cost. . 
Labor operating cost 



Y, 



0.033(Xr 0344 

o.oi7(xr - 295 



Equipment operating costs consist of 88% parts, 6% elec- 
tricity, and %'7( lubrication. Labor operating costs consist 
entirely of repair labor. 

Hopper Factor: In many installations, a vibrating 
feeder is not used, and pay gravel feeds directly from the 
hopper. If this is the case, no operating cost for feeders is 
required. 

Used Equipment Factor: If a feeder with over 10,000 
h of previous service life is to be used, the following factors 
must be applied to respective operating costs to account for 
increased maintenance and repair requirements: 

Equipment factor U e = 1.176 

Labor factor U, = 1.233 

Total Cost: Cost per cubic yard of feed is determined by 

[Y K (U.) + Y,(U,)]. 

The total cost per cubic yard must then be multiplied by 
total yearly amount of feed handled by feed hopper. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 6 for final operating cost 
calculation. 



0.010 



w 0.001 

















































































































































































"*"- Equ i pmen t 

1 

"**^> Labor 























10 100 1,000 

CRPRCITY, maximum cubic yards af feed treated per hour 

Processing operating costs - Feed hoppers 



OPERATING COSTS 



61 



PROCESSING— JIG CONCENTRATORS 



Operating Cost Equations: These equations provide 
the cost of gravity separation using jig concentrators. Costs 
are reported in dollars per cubic yard and include the 
operating cost of the jigs and associated drive motors. The 
equations are applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by jig concentrators. 

The base equations assume the following: 



100.000 



4. Slurry density, 40% 
solids. 

5. Gravity feed. 



1. Cleaner service. 

2. Hourly capacity, 0.617 
yd 3 /ft 2 . 

3. Feed solids, 3,400 
lb/yd 3 . 

Base Equations: 

Equipment operating cost. . . Y E = 0.113(Xr 0328 

Supply operating cost Y s = 0.002(X) _0 184 

Labor operating cost Y L = S^OSfX)" 1 268 

Equipment operating costs consist of 40% parts, 34% elec- 
tricity, and 26% lubrication. Supply operating costs consist 
entirely of lead shot for bedding material. Labor operating 
costs consist of 66% operator labor and 34% repair labor. 

Rougher-Coarse Factor: If jigs are to be used for 
rougher service or a coarse feed, higher productivity will 
be realized. To compensate for this situation, the following 
factor must be applied to total operating cost: 

F D = 0.344. 



I .000 



0. 100 





































































































































































































































































































































































































































































































































































































































































^.Equipment. 
x Labor 


























































































































































































































_Supp 


las 









0.1 1.0 10.0 100.0 1 ,000.0 

CRPRCITY, maximum cubic yards of fesd treated per hour 

Processing operating costs - Jig concentrators 



Used Equipment Factor: If jig concentrators with over 
10,000 h of service life are to be used, the following factors 
must be applied to respective operating costs to account for 
increased maintenance and repair requirements: 

Equipment factor U e = 1.096 

Labor factor U? = 1.087 



Total Cost: Cost per cubic yard of feed is determined by 

r s + Y L (U,)] x Fr . 



[Y E (U) + Y c 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of feed handled by jig concentrators. 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 6 for final operating cost 
calculation. 



62 



OPERATING COSTS 



PROCESSING— SLUICES 



Operating Cost Equations: These equations provide 
the cost of gravity separation using sluices. Costs are 
reported in dollars per cubic yard of feed and consist en- 
tirely of the expense of periodic concentrate cleanup. The 
equation is applied to the following variable: 

X = Maximum cubic yards feed handled hourly 
by sluice. 

The base equations assume the following: 



1. Steel plate 


4. 


Length-to-width ratio 


construction. 




4:1. 


2. Angle iron riffles. 


5. 


Gravity feed. 


3. Feed solids, 3,400 






lb/yd 3 . 







Base Equation: 

Labor operating cost ... Y, = 0.337(Xr° 6:ifi 

Labor operating costs consist entirely of feed adjustment 
and cleanup labor. Costs of maintenance labor and parts 
are negligible. 

Wood Sluice Factor: If wood sluices are to be used, 
an allowance must be made for periodic sluice replacement. 
To account for this, an equipment cost must be added to total 
cost, and labor cost must be multiplied by the following 
factor: 



Equipment cost Y E 

Labor factor W, 



0.00035(X) 0383 
1.141 



w O.OOI 





































































































































































































































































































































































"-Lctrar 





























































































1 10 100 1,000 

CRPRCITY, maximum cubic yards of feed treated per hour 

Processing operating costs - Sluices 



Total Cost: Cost per cubic yard of feed is determined by 

fY,(W,) + Y R ]. 

The total cost per cubic yard must then be multiplied by 
total yearly amount of feed handled by sluices. This product 
is subsequently entered in the appropriate row of the tabula- 
tion shown in figure 6 for final operating cost calculation. 



OPERATING COSTS 



63 



PROCESSING— SPIRAL CONCENTRATORS 



Operating Cost Equations: These equations provide 
the cost of gravity separation using spiral concentrators. 
Costs are reported in dollars per cubic yard of feed and in- 
clude the operating cost of the spirals and slurry splitters 
only. The equations are applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by spiral concentrators. 

The base equations assume the following: 



1. Rougher service. 

2. Solids per start, 1.75 
st/h. 

3. Feed solids, 3,400 
lb/yd 3 . 

Base Equations: 

Equipment operating cost . 
Labor operating cost 



4. Slurry density, 10% 
solids. 

5. Gravity feed. 



$0.0007/yd 3 
0.755(X)-°- 614 



Equipment operating costs consist entirely of parts. Labor 
operating costs consist entirely of operator labor, with the 
operator performing functions such as lining replacement. 

Cleaner-Scavenger Factor: If spirals are to be used 
for cleaning or scavenging, throughput is reduced. The 
following factors must be applied to respective operating 
costs: 

Equipment factor C e = 2.429 

Labor factor C, = 1.796 



S i.oooo 



. 1 000 



(X 
tr 

W 0.0001 



— 










_ 






















— 




























^Lc±io 




= 
































































































r 














































































































































































































































Equipment 































































































10 100 1,000 

CRPRCITY, maximum cubic yards of feed treated par hour 

Processing operating costs - Spiral concentrators 



Used Equipment Factor: Because spiral concentrators 
have no moving parts, they enjoy a long service life. 
Generally, only the liners require periodic replacement. For 
this reason, the operating costs asscociated with spirals are 
typically constant throughout the life of the machine. 

Total Cost: Cost per cubic yard of feed is determined by 

[0.0007(C e ) + Y L (C,)]. 

The total cost per cubic yard must then be multiplied by 
the total yearly amount of feed handled by spiral concen- 
trators. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



64 



OPERATING COSTS 



PROCESSING— TABLE CONCENTRATORS 



Operating Cost Equations: These equations provide 
the cost of gravity separation using table concentrators. 
Costs are reported in dollars per cubic yard of feed and in- 
clude the operating cost of the tables and associated drive 
motors. The equations are applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by table concentrators. 

The base equations assume the following: 

1. Cleaner service. 3. Slurry density, 25% 

2. Feed solids, 3,400 solids. 
lb/yd :i . 4. Gravity feed. 



10.00 



Base Equations: 

Equipment operating cost. 
Labor operating cost 



1.326(X)-o"43 
1.399(X)-0-783 



Equipment operating costs consist of 87% parts, 7% elec- 
tricity, and 6% lubrication. Labor operating costs consist 
of 67% operator labor and 33% repair labor. 

Rougher-Coarse Factor: If the tables are to be used 
for rougher service or a coarse feed, higher productivity will 
be realized. To compensate for this situation, the following 
factors must be applied to both equipment and labor 
operating costs: 

Equipment factor R e = 0.415 

Labor factor R, = 0.415 

Used Equipment Factor: If table concentrators with 
over 10,000 h of service life are to be used, the following 
factors must be applied to the respective operating costs to 
account for increased maintenance and repair requirements: 

Equipment factor U = 1.217(X)-° 002 

Labor factor U, = 1.12HX)- 0026 



1 .00 



























































































































































































































































































-"•Equl 


pment 


























































































^Lcfcor 






























1 





































































1 1.0 10.0 100.0 

D flCITY, maximum cubic yards of feed treated per hour 

Processing operating costs - Table concentrators 



Total Cost: Cost per cubic yard of feed is determined by 

[Y E (R e XU t .)+Y L (R,XU,)]. 

The total cost per cubic yard must then be multiplied by 
the total yearly amount of feed handled by table concen- 
trators. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



65 



PROCESSING— TAILINGS REMOVAL— BULLDOZERS 



Operating Cost Equations: These equations provide 
the cost of removing and relocating tailings using 
bulldozers. Costs are reported in dollars per cubic yard of 
tailings moved. The equations are applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, 
overburden, and tails moved hourly by 
bulldozer. 

The base equations assume the following: 

1. Efficiency, 50 min/h. 3. Average operator 

2. Dozing distance, 300 ability. 

ft. 4. Nearly level gradient. 



1 .000 



Base Equations: 

Equipment operating cost . 
Labor operating cost . . . . . 



Y E = 0.993(X)-°i30 
Y L = 14.01(X)-°945 



Equipment operating costs average 47% parts, and 53% fuel 
and lubrication. Labor operating costs average 86% operator 
labor and 14% repair labor. 

Distance Factor: If average dozing distance is other 
than 300 ft, the factor obtained from the following equa- 
tion must be applied to total cost per loose cubic yard: 

F D =0.00581(distance)0 904. 

Gradient Factor: If average gradient is other than 
level, the factor obtained from the following equation must 
be applied to total cost per loose cubic yard: 

Fr = 1.041e' 0015l P ercent gradient)]_ 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e =1.206(X)-°°i3 

Labor factor U, = 0.967(X)°oi5 

Total Cost: Cost per cubic yard of tailings is deter- 
mined by 

[Y E (U e ) + Y L fU,)] xF D xF G . 


















■ 


1 














— 


■ 






















































































"\Eq 


Liipment 




































Labor 

























10 100 1,000 

CAPACITY, maximum loose cubic yards per hour 

Processing operating costs - Tai I i ngs removal - Bui I dozers 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of tailings moved by bulldozer. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 6 for final operating cost 
calculation. 



tw 



OPERATING COSTS 



PROCESSING— TAILINGS REMOVAL— DRAGLINES 



Operating Cost Equations: These equations provide 
the cost of removing and relocating tailings using draglines. 
Costs are reported in dollars per cubic yard o f tailings 
moved. The equations are applied to the following variable: 

X = Maximum loose cubic yards of pay gravel, 
overburden, and tails moved hourly by 
dragline. 

The base equations assume the following: 

1. Bucket efficiency, 3. Swing angle, 90°. 



2. 



0.90. 
Full hoist. 



4. Average operator 
ability. 



Base Equations: 



Equipment operating cost. . 
Labor operating cost 



Y E = 1.984(X)-°-390 
Y,' = 12.19(X)-°888 



Equipment operating costs consist of 67% parts, 33% fuel 
and lubrication. Labor operating costs consist of 78% 
operator labor and 22% repair labor. 

Swing Angle Factor: If average swing angle is other 
than 90°, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F s =0.304(swing angle) 0269 . 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U c =1.162(X)-° 017 

Labor factor U, = 0.989(X)°oo6 











































































^*"""-- Equipment 
























































^ Lc±)or 



































































10 100 1,000 

CAPACITY, maximum loose cubic yards per hour 

Processing operating costs - Tai I i ngs removal - Dragl i nes 






Total Cost: Cost per cubic yard of feed is determined by 

[Y E (U e ) + Y L (U,)] xF s . 

The total cost per cubic yard must then be multiplied by 
the total yearly amount of tailings moved by dragline. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 6 for final operating cost 
calculation. 



OPERATING COSTS 



67 



PROCESSING— TAILINGS REMOVAL— FRONT-END LOADERS 



Operating Cost Equations: These equations provide 
the cost of removing and relocating tailings using wheel- 
type front-end loaders. Costs are reported in dollars per 
cubic yard of tailings moved. The equations are applied to 
the following variable: 

X = Maximum loose cubic yards of pay gravel, 
overburden, and tails moved hourly by 
front-end loader. 

The base equations assume the following: 

1. Haul distance, 500 ft. 3. Inconsistent operation. 

2. Rolling resistance, 2%, 4. Wheel-type loader, 
nearly level gradient. 



1 .QQQ 



Base Equations: 

Equipment operating cost . . 
Labor operating cost 



Y E = 0.407(X)-0-225 
Y L = 13.07(X)"0-936 



Equipment operating costs average 22% parts, 46% fuel and 
lubrication, and 32% tires. Labor operating costs average 
90% operator labor and 10% repair labor. 

Distance Factor: If average haul distance is other than 
500 ft, the factor obtained from the following equation must 
be applied to total cost per loose cubic yard: 

F D =0.023(distance) 0616 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F r = 0.877e [0046( P ercent gradient>]_ 

































































































Equipment 


























































Labor 















































O.OIO 

10 100 1,000 

CRPRCITY, maximum loose cubic yards per hour 
Processing operating costs - tai I i ngs removal - Front-end loaders 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e =1.162(X)-° 017 

Labor factor U!=0.989(X) oo6 

Track-Type Loader Factor: If track-type loaders are 
used, the following factors must be applied to total cost ob- 
tained from the base equations: 

Equipment factor T e = 1.378 

Labor factor T,=1.073 



by 



Total Cost: Cost per cubic yard of tailings is determined 



[Y E fU e XT e )+Y L (U,XT,)] x F D x F G . 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of tailings moved by front-end 
loader. This product is subsequently entered in the ap- 



propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



68 



OPERATING COSTS 



PROCESSING— TAILINGS REMOVAL— REAR-DUMP TRUCKS 



Operating Cost Equations: These equations provide 
the cost of removing and relocating tailings using rear-dump 
trucks. Costs are reported in dollars per cubic yard of tail- 
ings moved. The equations are applied to the following 
variable: 

X = Maximum loose cubic yards of pay gravel, 

overburden . and tails moved hourly by rear- 
dump truck. 

The base equations assume the following: 

1. Haul distance, 4. Average operator 



I .000 



2,500 ft. 

2. Loader cycles to fill, 4. i 

3. Efficiency, 50 min/h. 

Base Equations: 

Equipment operating cost. 
Labor operating cost 



ability. 

Rolling resistance, 2%, 

nearly level gradient. 



Y E = 0.602(X)-0296 
Y L = 11.34(X)-o.89i 



Equipment operating costs consist of 28% parts, 58% fuel 
and lubrication, and 14% tires. Labor operating costs con- 
sist of 82% operator labor and 18% repair labor. 

Distance Factor: If average haul distance is other than 
2,500 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

Fi^O.OgSfdistance) -'". 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 2%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

F ( . = 0.907e |lu)49l P l ' lc '' nt Kradicntll. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of the base operating costs must 
be multiplied by factors obtained from the following 
equations: 

Equipment factor U e =0.984(X)°° 1 6 

Labor factor U I = 0.943(X) 0021 

Total Cost: Cost per cubic yard of tailings is deter- 
mined by 

[Y E (U e )+Y L (U,)] xF D xF G . 



0. 100 





















































































































Equipment 




































\ Labor 













































10 1 00 1 , 000 

CAPACITY, maximum loose cubic yards per hour 

Processing operating costs - Tai I ings removal - Rear-dump trucks 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of tailings moved by truck. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 6 for final operating cost 
calculation. 



OPERATING COSTS 



69 



PROCESSING— TAILINGS REMOVAL— SCRAPERS 



Operating Cost Equations: These equations provide 
the cost of removing and relocating tailings using scrapers. 
Costs are reported in dollars per cubic yard of tailings 
moved. The equations are applied to the following variable: 

X = Maximum loose cubic yards of pay gravel, over- 
burden, and tails moved hourly by scraper. 



The base curves assume the following: 
1. Standard scrapers. 4. 



.000 



Rolling resistance, 6%, 
nearly level gradient. 
Efficiency, 50 min/h. 



Base Equation: 

Equipment operating cost . 
Labor operating cost 



Haul distance, l.UUU 

ft. 


oi 



Average operator 
ability. 



"O 

Ul 

□ 
u 


Y E = 0.325(X)- 0210 


ID 

z 

r- 

(X 



12.0KX)- 0930 



Equipment operating costs consist of 48% fuel and lubrica- 
tion, 34% tires, and 18% parts. Labor operating costs con- 
sist of 88% operator labor and 12% repair labor. 

Distance Factor: If average haul distance is other than 
1,000 ft, the factor obtained from the following equation 
must be applied to total cost per loose cubic yard: 

F D = 0.01947(distance) 0577 . 

Gradient Factor: If total gradient (gradient plus roll- 
ing resistance) is other than 6%, the factor obtained from 
the following equation must be applied to total cost per loose 
cubic yard: 

JT =0 77fie'0-0 47, P ercent gradient)] 



i ou 





















































































































Equ 1 pmen t 
























































Labor 

























10 100 1,000 

CAPACITY, maximum loose cubic yards per hour 

Processing operating costs - Tai i ings removal - Scrapers 



Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by factors obtained from the following equations: 



Equipment factor U 



1.096(X) 



-0.006 

Labor factor U~ = 0.845(X) 0034 

Total Cost: Cost per cubic yard of tailings is determin- 

[Y E (U e ) + Y L (U,)] x F D x F G . 

The total cost per cubic yard must then be multiplied by 
total yearly amount of tailings moved by scraper. This 
product is subsequently entered in the appropriate row of 
the tabulation shown in figure 6 for final operating cost 
calculation. 



OPERATING COSTS 



PROCESSING— TROMMELS 



Operating Cost Equations: These equations provide 
the cost of processing gravel using trommels. Costs are 
reported in dollars per cubic yard of gravel handled. The 
equations are applied to the following variable: 

X = Maximum cubic yards of gravel processed 
hourly by trommels. 

The base equations assume the following: 

1. Trommels are sec- 2. Associated electric 

tioned for scrubbing motor operating costs 

and sizing. 



are included. 



Base Equations: 



-0.403 



Equipment capital cost Y E = 0.217(X) 

Labor operating cost Y,' = 0.129(X)-° 429 

Equipment operating costs average 63% parts, 26% elec- 
tricity, and 11% lubrication. Labor operating costs consist 
entirely of maintenance and repair labor. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by the following factors: 

Equipment factor U = 1.194 

Labor factor U, = 1.310 

Total Cost: Cost per cubic yard of gravel is determin- 
ed bv 

[Y R (U.) + Y,(U,)]. 

The total cost per cubic yard must then be multiplied by 
the total yearly amount of gravel processed by trommels. 
This product is subsequently entered in the appropriate row 
of the tabulation shown in figure 6 for final operating cost 
calculation. 



a 












































T3 
CD 
ID 






















O 










^"N 












L 


O 




































^"*** Equ I pmsn t 


1 



L 0.010 




































^"^ Labor 


























co 






















a 













































■a 






















H 

a 

CJ 






















z 






















1- 
(X 

w 0.001 






















3 








100 








! ,0 



CAPACITY, max i mum cubic yards af feod treated per hour 



Processing operating costs - Trommels 



OPERATING COSTS 



71 



PROCESSING— VIBRATING SCREENS 



Operating Cost Equations: These equations provide 
the cost of processing gravel using vibrating screens. Costs 
are reported in dollars per cubic yard of gravel handled. The 
equations are applied to the following variable: 

X = Maximum cubic yards of gravel processed 
hourly by vibrating screen. 

The base equations assume the following: 

1. An average of 0.624 
ft 2 of screen is re- 
quired for every cubic 
yard of hourly 
capacity. 



Base Equations: 

Equipment operating cost 
Labor operating cost 



Equipment operating costs average 73% parts, 19% elec- 
tricity, and 8% lubrication. Labor operating costs consist 
entirely of maintenance and repair labor. 

Capacity Factor: If anticipated screen capacity is other 
than 0.624 ft 2 /yd 3 hourly feed capacity, the respective 
operating costs must be multiplied by factors obtained from 
the following equations: 

C = 1.267(C) 0575 , 



<B o. ioo 



2. 


Associated electric 


3 
O 


ic 

3. 

4. 


motor operating costs 
are included. 
Feed solids, 3,120 
lb/yd 3 . 
Gravity feed. 




a 

01 

i_ 
a 



■o 

Ul 
D 


cost. . 


. Y E = 0.104(Xr 0426 
. Y L = 0.106(X)-°- 570 


19 

Z 

1- 
I 

w 0.00 









































































































































^^ Equ i pmsn t 




































Labor 

























10 100 I ,000 

CRPflCITY, maximum cubic yards of feed treated per hour 

Processing operating costs - Vibrating screens 



and 

C, = 1.207(C) 0458 , 

where C = anticipated capacity in square feet of screen per 
cubic yard of hourly feed. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by the following factors: 



Equipment factor U 



1.197 



Labor factor U, = 1.131 



Total Cost: Cost per cubic yard of gravel is deter- 
mined by 

[Y E (C e XU e ) + Y L (C,XU,)]. 

The total cost per cubic yard must then be multiplied by 
the total yearly amount of gravel processed by the vibrating 
screen. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



72 



OPERATING COSTS 



SUPPLEMENTAL— EMPLOYEE HOUSING 



Operating Cost Equation: This equation furnishes the 
operating cost associated with providing housing for 
workers at the minesite. Costs are reported in dollars per 
loose cubic yard of overburden and pay gravel. Expenses 
for food, supplies, water, heat, and electricity are all taken 
into account. The equation is applied to the following 
variable: 

X = Average loose cubic yards of overburden and 
pay gravel handled hourly. 

The base equation assumes the following: 
1. Shift. 10 h. 

Base Equation: 

Supply operating cost. . . Y s = 1.445(X)-°- 583 

Supply operating costs average 95% industrial materials 
and 5 c /( fuel. 

Food Allowance Factor: If workers are to pay for food 
and supplies out of their own pockets, the cost calculated 
from the above equation must be multiplied by the follow- 
ing factor: 

F F = 0.048. 

Workforce Factor: The equation used to compute labor 
for operating cost estimation is 

Workforce = 0.822(X) 0415 . 



1 .000 






































= 


— ' 


























































100 








































































































^Suppl i 


3S 


0.010 






















10 








100 








1 ,0 



Cf-IPflC I TY , average loose cubic yards pay 
gravel plus overburden mined per hour 

Supplemental operating costs - Employee housing 



If the workforce for the operation under evaluation is 
known, and is different than that calculated from the above 
equation, the correct cost can be obtained from the follow- 
ing equation: 

(Number of workers) x $17.85 

s 

Cubic yards of overburden and pay gravel 

handled daily 

Total Cost: Cost per loose cubic yard is determined by 

Y s x F F . 

The total cost per loose cubic yard must then be multiplied 
by the total yearly amount of overburden and pay gravel 
handled. This product is subsequently entered in the ap- 
propriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



73 



SUPPLEMENTAL— GENERATORS 



Operating Cost: Operating costs of diesel generators 
are accounted for in the electrical portions of the other 
equipment operating costs. By so doing, operating costs of 
the generators are tied directly to size and type of equip- 
ment used. 

The electrical portions of operating cost curves will also 



account for the expense of electricity brought in through 
transmission lines if diesel generators are not used. This 
is at best an approximation. However, costs assigned in this 
manner are typically more representative than costs 
calculated by trying to estimate the total power consump- 
tion of an operation. 



74 



OPERATING COSTS 



SUPPLEMENTAL— LOST TIME AND GENERAL SERVICES 



Operating Cost Equations: These equations account 
for costs not directly related to production. Costs are 
report fd m dollars per cubic yard. Items in this section 
include: 

1. Equipment downtime. 

a . Productivity lost by the entire crew due to 
breakdown of key pieces of equipment. 

b. Productivity lost by individual operators due to 
breakdown of single pieces of equipment. 

c. Labor charges of outside maintenance personnel. 
d . Wash plant relocation. 

2. Site maintenance. 

a . Road maintenance. 

b. Stream diversion. 

c . Drainage ditch construction and maintenance. 

d . Site cleanup. 

e . Reclamation grading and recontouring. 

f . Settling pond maintenance. 

3. Concentrate refinement. 

a . Time spent recovering valuable minerals from mill 
concentrates by panning, mechanical separation, or 
amalgamation. 

The equations are applied to the following variable: 

X = Maximum cubic yards of feed handled hourly 
by mill. 



I .000 



(0 . 1 00 





































































































ant 
















•-v^ Labor 







































































































0.010 

10 100 1,000 

MILL CAPACITY, maximum cubic yards of feed treated per hour 
Supplemental operating costs - Lost time and general services 



Base Equations: 

Equipment operating cost . 
Labor operating cost 



Y E = 0.142(X) 0004 
Y,; = 2.673(X)" 0524 



Equipment operating costs average 53% fuel and lubrica- 
tion and 47% equipment parts. Labor operating costs con- 
sist of 91% operator labor and 9% maintenance and repair 
labor. 

Total Cost: Cost per cubic yard is determined by 



The total cost per cubic yard must then be multiplied by 
the total yearly amount of overburden, pay gravel, and tail- 
ings handled. This product is subsequently entered in the 
appropriate row of the tabulation shown in figure 6 for final 
operating cost calculation. 



OPERATING COSTS 



75 



SUPPLEMENTAL— PUMPS 



Operating Cost Equations: These equations provide 
the cost of transporting and providing water using cen- 
trifugal pumps. Costs are reported in dollars per hour of 
pump use. If more than one pump is used in the operation, 
a separate cost must be calculated for each. The equations 
are applied to the following variable: 

X = Maximum gallons of water required per 
minute. 

The base equations assume the following: 



1. Total head, 25 ft. 

2. Diesel-powered pumps. 



3. Abrasion-resistant 
steel construction. 

4. Total engine-pump ef- 
ficiency, 60%. 



Base Equations: 

Equipment operating cost . 
Labor operating cost 



Y E = 0.007(X) - 713 
Y, = 0.004(X) 0867 



Equipment operating costs average 59% fuel and lubrica- 
tion, and 41% parts. Labor operating costs consist of 82% 
operator labor and 18% maintenance and repair labor. 
(Operator labor includes pipeline work.) 

Head Factor: If total pumping head is other than 25 
ft, factors calculated from the following equations will cor- 
rect for changes in equipment and labor operating costs. 
The product of these factors and the original costs will pro- 
vide the appropriate figures: 



H = 0.091(H) 0735 , 



and 



H, = 0.054(H) 0893 

where H = total pumping head. 

Used Equipment Factor: These factors account for 
added operating expenses accrued by equipment having 
over 10,000 h of previous service life. The respective equip- 
ment and labor portions of base operating costs must be 
multiplied by the following factors: 

Equipment factor U = 1.096 

Labor factor U* = 1.067 

Total Cost: Cost per hour is determined by 

[Y F (H XU )] + [Y T (H,XU,)]. 



o. 10 























































































Labor 




























Equ 


pment 













































































































































































































































































































































10 100 1,000 10,000 

PUMP CAPACITY, maximum gal Ions per minute 

Supplemental operating costs - Pumps 



The total cost per hour must then be multiplied by the an- 
ticipated hours per year of pump use. This product is subse- 
quently entered in the appropriate row of the tabulation 
shown in figure 6 for final operating cost calculation. 



76 



CAPITAL COST SUMMARY FORM 

Item Cost 

Exploration: 

Method 1 cost $ 

Method 2 cost 

Development: 

Access roads 

Clearing 

Preproduction overburden removal: 

Bulldozers 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Mine equipment: 

Backhoes 

Bulldozers 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Processing equipment: 

Conveyors 

Feed hoppers 

Jig concentrators 

Sluices 

Spiral concentrators 

Table concentrators 

Trommels 

Vibrating screens 

Supplemental: 

Buildings 

Camp 

Generators 

Pumps 

Settling ponds 

Subtotal 

Contingency (10%) 

Total ^^ = ^^ = 

Figure 5.— Capital cost summary form. 



77 



OPERATING COST SUMMARY FORM 

Item Annual cost 

Overburden removal: 

Bulldozers $ 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Mining: 

Backhoes 

Bulldozers 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Processing: 

Conveyors 

Feed hoppers 

Jig concentrators 

Sluices 

Spiral concentrators 

Table concentrators 

Tailings removal: 

Bulldozers 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Trommels 

Vibrating screens 

Supplemental: 

Employee housing 

Lost time and general services 

Pumps 

Subtotal 

Contingency (10%) 

Total 



Cost per cubic yard pay gravel = total annual cost divided by pay gravel mined per year. 
Final cost per cubic yard pay gravel 

Figure 6.— Operating cost summary form. 



TS 



BIBLIOGRAPHY 



Caterpillar Tractor Co. Peoria, IL. Caterpillar Performance Hand- 
book l.uh ed., 1984, 600 pp. 

Dataquest Inc. Cost Reference Guide for Construction Equipment. 
Equipment Guide Book Co., Palo Alto, Ca. Periodically upated. 

Godfrey, R.S. Means Building Construction Cost Data, 1935. 
Robert Snow Means Co.Inc, Kingston, MA. 43d ed., 1984, 455 pp. 

Marshall and Swift (Los Angeles, CA). Marshall Valuation Serv- 
ice. Periodically updated. 



Richardson Engineering Services, Inc. (San Marcos, CA). Process 
Plant Construction Estimating Standards. Periodically updated. 

Schumacher, O.L. Mining Cost Service. Western Mine Eng., 
Spokane, WA, periodically updated. 

Terex Corp. (Hudson, OH). Production and Cost Estimating of 
Material Movement With Earthmoving Equipment. 1981, 78 pp. 









79 



APPENDIX.— EXAMPLE OF COST ESTIMATE 

SAMPLE ESTIMATION 
Parameters 



General: 
150 operating d/a. 
10 h/shift. 

100-LCY/h pay gravel capacity. 
2.5-LCY stripping ratio. 
150,000 LCY/a pay gravel mined. 
375,000 LCY/a overburden removed. 
Workers live on site. 

Exploration: 
20 worker-days reconnaissance. 
1,400 ft churn drilling. 
2,000 yd 3 trenching 
1,200 samples panned. 
8 h helicopter time. 
180 worker-days camp requirements. 

Development: 
4-mile access road. 
20% side slope. 
Forested. 
22 ft wide. 
Ungraveled. 
6 acres cleared. 
Forested. 
10% side slope. 

Overburden removal: 
Excavated and hauled by 1 scraper. 
250-LCY/h production capacity. 
330,000 LCY prior to production. 
3,000-ft average haul distance. 
+8% average haul gradient. 



Mining: 
Excavation by 1 backhoe. 
Hauled by 2 front-end loaders. 
100-LCY/h production capacity. 
Medium-hard digging. 
800-ft average haul length. 
+6% average haul gradient. 



Mine equipment: 
1 new backhoe. 

1 used bulldozer. 

2 new front-end loaders. 
1 used scraper. 



Milling (jig plant, see figure A-l): 
Feeder, 100 LCY/h. 
Trommel, 100 LCY/h. 
Rougher jig, 20 yd 3 /h. 
Cleaner jigs, 2 at 5 yd 3 /h. 
Final jig, 0.2 yd 3 /h. 
Scavenger sluice, 50 yd 3 /h. 
Scavenger sluice, 20 yd 3 /h. 
Conveyor, 70 yd 3 /h, 40 ft. 

Tailings placement: 
Transported using 1 bulldozer. 
100-LCY/h production capacity. 
400-ft average haul length. 
-8% average gradient. 



Escalation Factors (January to July 1985) 

Labor 11.98/11.69 = 1.025 

Equipment 362.3/360.4 = 1.005 

Steel , 354.6/357.4 = 0.992 

Lumber 354.9/343.2 = 1.034 

Fuel : 630.7/636.2 = 0.991 

Tires 246.0/262.0 = 0.939 

Construction materials 363.63/358.32 = 1.015 

Electricity 540.3/524.9 = 1.029 

Industrial materials 324.3/323.2 = 1.003 



so 



Front-end loader 



Waste 4- 



Waste 4- 



Conveyor 



Dump 



Minus 0.5 in 
(50 yd 3 /h) 



Sluice 



Concentrate 
(0.01 yd 3 /h) 

r> 



Mine-run gravel 
(100 yd 3 /h) 







Feed hopper 












Oversize 


Trommel 




(25 yd 3 /h) m 


■* 










fe. 




^ 






w 



Minus 0.25 in 
(20 yd 3 /h) 



Rougher jig 



Concentrate 
(5 yd 3 /h) 

r-\ 



Cleaner jig 



Concentrate 
(0.1 yd 3 /h) 



Final jig 



Concentrate 
(0.03 yd 3 /h) 



Panning 



Gold product 



_^ Waste — _ 
(20 yd 3 /h) *~ 



Sluice 



Concentrate 
(0.01 yd 3 /h) 



S\ 



Minus 0.125 in 
(5 yd 3 /h) 



Cleaner jig 



Concentrate 
(0.1 yd 3 /h) 



Figure A-1— Sample flow sheet. 



CAPITAL COSTS 



81 



Exploration (p. 20) 

Reconnaissance 20 worker-days x $195/worker-day = $3,900 

Churn drilling 1,400 ft x $45/ft = 63,000 

Trenching 2,000 yd 3 x $7.10/yd 3 = 14,200 

Panning 1,200 samples x $2.10/sample = 2,520 

Helicopter 8 h x $395/h = 3,160 

Camp 180 worker-days x $30/worker-day = 5,400 

Exploration capital cost = $92,180 x 1.025 (labor) 



$94,485 



Access roads (p. 22) 

22-ft wide 
4 miles long 
20% side slope 
Forested 
600 ft blasting 

Base cost Y c = 765.65(22)° 922 = 

Labor $13,236 x 0.68 x 1.025 = 

Parts $13,236 x 0.13 x 1.005 = 

Fuel $13,236 x 0.16 x 0.991 = 

Tires $13,236 x 0.03 x 0.939 = 

Forest factor F F = 2.000(22)-° 079 = 

Side slope factor Fg = 0.633e [0021(20)] = 

Blasting factor F H = [12,059.18(22)°- 534 ] x (600/5,280) = 

Access road capital cost = [($13,426 x 1.567 x 0.963 x 4] + 7,140 



$13,236/mile 

$9,225 

1,729 

2,099 

373 



$13,426/mile 

1.567 
0.963 
7,140 



$88,180 



Clearing (p. 23) 



6 acres 

10% side slope 

Forested 

Base cost Y r = 1,043.61(6)°- 913 



$5,358 



Labor $5,358 x 0.68 x 1.025 

Parts $5,358 x 0.12 x 0.991 

Fuel $5,358 x 0.18 x 1.006 

Steel $5,358 x 0.02 x 0.992 



Slope factor F g 

Forest factor F 



9 42e [0.008(10)] 
F 



$3,735 
637 
970 
106 

$5,448 

1.020 
1.750 



Clearing capital cost = [$5,448 x 1.020 x 1.750] 



$9,725 



82 



Preproduction overburden removal (p. 24) 

30,000 LCY 

250 LCY/h 

3.000-ft haul 

+ 8% haul gradient plus rolling resistance 

Used scraper 

Equipment cost Y E = 0.325(250)-°- 21 ° = $0.102/LCY 

Parts $0,102 x 0.18 x 1.005 = $0,018 

Fuel and lubrication $0,102 x 0.48 x 0.991 = 0.049 

Tires $0,102 x 0.34 x 0.939 = 0.033 

$0.100/LCY 

Labor cost Y L = 12.01(250r°- 93 ° = $0.071/LCY 

Labor $0,071 x 1.00 x 1.025 = $0.073/LCY 

Distance factor F D = 0.01947(3,000)°- 577 = 1.975 

Gradient factor F G = 0.776e [0047(8)] = 1.130 

Used equipment U e = 1.096(250)-° 006 = 1.060 

U[ = 0.845(250)° ° 34 = 1.019 

Overburden removal capital cost = [($0,100 x 1.060) + ($0,073 x 1.019)] x 1.975 x 1.130 x 
30,000 $12,077 



Mine equipment— backhoes (p. 29) 

100 LCY/h 

80% maximum digging depth 

Medium-hard digging 

Base cost Y r 



84,132.01e [0 ° 0350<1 °° )] 



Equipment $119,389 x 1.00 x 1.005 

Digging depth factor F D = 0.04484(80)°- 790 

Digging difficulty factor F H 



= $119,389 

= $119,986 

1.429 
1.556 



Backhoe capital cost = ($119,986 x 1.429 x 1.556) $266,792 



Mine equipment— bulldozers (p. 30) 

100 LCY/h 

400-ft average haul distance 
-8% average haul gradient 
Used equipment 

Base cost Y c = 3,555.96(100)°- 806 

Equipment $145,531.00 x 1.00 x 1.005 

Distance factor F D = 0.01549(400)°- 732 

Gradient factor F G = 1.041e [0015( - 8)] 

Used equipment factor Fjj 

Bulldozer capital cost = ($146,259 x 1.244 x 0.923 x 0.411) . 



= $145,531 

= $146,259 

1.244 
0.923 
0.411 



$69,022 



83 



Mine equipment— front-end loaders (p. 32) 

100 LCY/h 

Two machines, 50 yd 3 /h each 

800-ft average haul 

+ 6% haul gradient plus rolling resistance 

Base cost Y c = 2,711.10(50)° 896 = $90,245 

Equipment $90,245 x 1.00 x 1.005 = $90,696 

Distance factor F D = 0.033(800)°- 552 = 1.321 

Gradient factor F G = 0.888e t0041(6)) = 1.136 

Front-end loader capital cost = (2 x $90,696 x 1.321 x 1.136) $272,207 

Mine equipment— scrapers (p. 34) 

250 LCY/h 

3,000-ft average haul 

+8% haul gradient plus rolling resistance 

Used equipment 

Base cost Y c = 1,744.42(250) - 934 = $302,919 

Equipment = $302,919 x 1.00 x 1.005 = $304,434 

Distance factor F D = 0.025(3,000) - 539 = 1.871 

Gradient factor F G = 0.776e [0047(8)] = 1.130 

Used equipment factor Fjj = 0.312 

Scraper capital cost = ($304,434 x 1.871 x 1.130 x 0.312) $200,817 

Processing equipment— conveyors (p. 35) 

70 ydVh 

40 ft long 

Base cost Y c = 4,728.36(70)°- 287 = $16,005 

Equipment price $16,005 x 0.89 x 1.005 = $14,316 

Installation labor $16,005 x 0.08 x 1.025 = 1,312 

Construction materials $16,005 x 0.03 x 1.015 = 487 

Conveyor capital cost = ($14,316 + $1,312 + $487) $16,115 

Processing equipment— feed hoppers (p. 36) 

100 yd7h 

Base cost Y c = 458.48(100)° 47 ° = $3,993 

Equipment price $3,993 x 0.82 x 1.005 = $3,291 

Installation labor $3,993 x 0.14 x 1.025 = 573 

Steel $3,993 x 0.04 x 0.992 = 158 

Feed hopper capital cost = ($3,291 + $583 + $158) $4,022 



84 



Processing equipment— rougher jig (p. 37) 

20 ydVh 

Base cost Y c = 6,403.82(20)°- 595 = $38,067 

Equipment price $38,067 x 0.62 x 1.005 = $23,720 

Installation labor $38,067 x 0.12 x 1.025 = 4,682 

Construction materials $38,067 x 0.26 x 1.015 = 10,046 

Rougher factor F R = 0.531 

Rougher jig capital cost = [($23,720 + $4,682 + $10,046) x 0.531] $20,416 

Processing equipment— cleaner jigs (p. 37) 

2 at 5 ydVh 

Base cost Y c = 6,403.82(5) 0595 = $16,685 

Equipment price $16,685 x 0.62 x 1.005 = $10,396 

Installation labor $16,685 x 0.12 x 1.025 = 2,052 

Construction materials $16,685 x 0.26 x 1.015 = 4,403 

Cleaner jigs capital cost = [$10,396 + $2,052 + $4,403) x 2] $33,702 

Processing equipment— final jig (p. 37) 

0.2 ydVh 

Base cost Y c = 6,403.82(0.2) - 595 = $2,458 

Equipment price $2,458 x 0.62 x 1.005 = $1,532 

Installation labor $2,458 x 0.12 x 1.025 = 302 

Construction materials $2,458 x 0.26 x 1.015 = 649 

Final jig capital cost = ($1,532 + $302 + $649) $2,483 

Processing equipment— sluice (p. 38) 

50 yd 3 /h 

Base cost Y c = 113.57(50)° 567 = $1,044 

Construction labor $1,044 x 0.61 x 1.025 = $653 

Construction materials $1,044 x 0.39 x 1.015 = 413 

Sluice capital cost = ($653 + $413) . $1,066 

Processing equipment— sluice (p. 38) 

20 ydVh 

Base cost Y c = 113.57(20)°- 567 = $621 

Construction labor $621 x 0.61 x 1.025 = $388 

Construction materials $621 x 0.39 x 1.015 = 246 

Sluice capital cost = ($388 + $246) $634 



85 



Processing equipmment— trommel (p. 41) 

100 LCY/h 

Base cost Y c = 7,176.21(100)°- 559 

Equipment price $94,166 x 0.64 x 1.005 

Installation labor $94,166 x 0.26 x 1.025 

Construction materials $94,166 x 0.10 x 1.015 

Trommel capital cost = ($60,568 + $25,095 + $9,558) 



$94,166 

$60,568 

25,095 

9,558 



$95,221 



Supplemental— main building (p. 43) 

1,680 ft 2 
Cement floor 
Plumbing added 

Base cost Y c = 34.09(1,680)°- 907 = $28,707 

Equipment $28,707 x 0.25 x 1.005 = $7,213 

Construction labor $28,707 x 0.34 x 1.025 = 10,004 

Construction materials $28,707 x 0.41 x 1.015 = 11,946 

Cement floor factor F c = 1.035(1,680) 0008 = 1.098 

Plumbing factor F p = 1.013(1,680) 0002 = 1.028 

Main building capital cost = [($7,213 + $10,004 + $11,946) x 1.098 x 1.028] 



$32,918 



Supplemental— sheds (p. 43) 

2 at 216 ft 2 each 

Base cost Y c = 34.09(216) - 907 

Equipment $4,467 x 0.25 x 1.005 

Construction labor $4,467 x 0.34 x 1.025 

Construction materials $4,467 x 0.41 x 1.015 

Shed capital costs = [($1,122 + $1,557 + $1,859) x 2] 



$4,467 

$1,122 
1,557 
1,859 



$9,076 



Supplemental— employee housing (p. 44) 

100 LCY/h pay gravel 
250 LCY/h overburden 
350 LCY/h total 
Used trailers 

Base cost Y c = 7,002.51(350)° 418 = $81,035 

Equipment $81,035 x 0.90 x 1.005 = $73,296 

Construction labor $81,035 x 0.07 x 1.025 = 5,814 

Construction materials $81,035 x 0.03 x 1.015 = 2,468 

Used trailer factor Fy = 0.631 

Employee housing capital cost = [($73,296 + $5,814 + $2,468) x 0.631] . . 



$51,476 



86 



Supplemental— generators (p. 45) 

100-LCY/h mill feed 

Base cost Y c = 1,382.65(100) - 604 = $22,321 

Equipment $22,321 x 0.75 x 1.005 = $16,824 

Construction labor $22,321 x 0.19 x 1.025 = 4,347 

Construction materials $22,321 x 0.06 x 1.015 = 1,359 

Generator capital cost = ($16,824 + $4,347 + $1,359) $22,530 



Supplemental— pumps (p. 46) 

100-LCY/h mill feed 
80-ft head 

Water consumption (p. 47) = 94.089Q00) - 546 = 1,163 gpm 

Base cost Y c = 63.909(1,163)° 618 = $5,013 

Equipment $5,013 x 0.70 x 1.005 = $3,527 

Installation labor $5,013 x 0.08 x 1.025 = 411 

Construction materials $5,013 x 0.22 x 1.015 = 1,120 

Head factor F H = 0.125(80)°- 637 = 2.038 

Pump capital cost = [($3,527 + $411 + $1,120) x 2.038] $10,308 

Supplemental— settling ponds (p. 47) 

1,163 gpm 

Base cost Y c = 3.982(1,163)°- 952 = $3,300 

Construction labor $3,300 x 0.75 x 1.025 = $2,537 

Fuel and lubrication $3,300 x 0.13 x 0.991 = 425 

Equipment parts $3,300 x 0.12 x 1.005 = 397 

Settling pond capital cost = ($2,537 + $425 + $397) $3,360 



87 



CAPITAL COST SUMMARY FORM 

Item Cost 

Exploration: 

Method 1 cost $ 

Method 2 cost 94,485 

Development: 

Access roads 88,180 

Clearing 9,725 

Preproduction overburden removal: 

Bulldozers 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 1 2,077 

Mine equipment: 

Backhoes 266,792 

Bulldozers 69,022 

Draglines 

Front-end loaders 272,207 

Rear-dump trucks 

Scrapers 200,81 7 

Processing equipment: 

Conveyors 16,115 

Feed hoppers 4,022 

Jig concentrators 56,601 

Sluices 1 ,700 

Spiral concentrators 

Table concentrators 

Trommels 95,221 

Vibrating screens 

Supplemental: 

Buildings 41 ,994 

Camp 51 ,476 

Generators 22,530 

Pumps 1 0,308 

Settling ponds 3,360 

Subtotal 1,316,632 

Contingency (1 0%) 131,663 

Total 1,448,295 

Figure A-2.— Capital cost summary form completed for example estimation. 



S8 



OPERATING COSTS 



Overburden removal— scrapers (p. 52) 

250 LCY/h 

3,000-ft average haul distance 

+8% average haul gradient plus rolling resistance 

Used equipment 

Equipment Y E = 0.325(250)-°- 210 = $0.102/LCY 

Parts $0,102 x 0.18 x 1.005 = $0,018 

Fuel and lubrication $0,102 x 0.48 x 0.991 = 0.049 

Tires $0,102 x 0.34 x 0.939 = 0.033 

$0,100 

Labor Y L = 12.01(250)-°- 930 = $0.071/LCY 

Labor $0,071 x 1.00 x 1.025 = $0,073 

Distance factor F D = 0.01947(3,000) - 577 = 1.975 

Gradient factor F G = 0.776e [0047(8)! = 1.130 

Used equipment factor U e = 1. 096(250)" 0006 = 1.060 

U, = 0.845(250) 0034 = 1.019 

Overburden removal cost [(0.100 x 1.060) + (0.073 x 1.019)] x 1.975 x 1.130 = $0.403/LCY 

Annual scraper operating cost = $0.403/LCY x 375,000 LCY/a $151,125 



Mining— backhoes (p. 53) 

Pay gravel excavation 

100 LCY/h 

80% maximum digging depth 

Medium-hard digging difficulty 

Equipment Y E = 8.360(100r 1019 = $0.077/LCY 

Parts $0,077 x 0.38 x 1.005 = $0,029 

Fuel and lubrication $0,077 x 0.62 x 0.991 = _ 0.047 

$0,076 

Labor Y L = 17.53(100r 1009 = $0.168/LCY 

Labor $0,168 x 1.00 x 1.025 = $0,172 

Digging depth factor F D = 0.09194(80) 0608 = 1.320 

Digging difficulty factor F H = 1.500 

Backhoe mining cost = [(0.076 + 0.172)] x 1.320 x 1.500 = $0.491/LCY 

Annual backhoe operating cost = $0.491/LCY x 150,000 LCY/a 



$73,650 



89 



Mining— front-end loaders (p. 56) 

Pay gravel haulage 

100 LCY/h total 

Two 50-LCY/h loaders 

800-ft average haul distance 

+ 6% average haul gradient plus rolling resistance 

Equipment Y E = 0.407(50)" - 225 = $0.169/LCY 

Parts $0,169 x 0.22 x 1.005 = $0,037 

Fuel and lubrication $0,169 x 0.46 x 0.991 = 0.077 

Tires $0,102 x 0.32 x 0.939 = 0.051 

$0,165 

Labor Y L = 13.07(50)-°- 936 = $0.336/LCY 

Labor $0,336 x 1.00 x 1.025 = $0,344 

Distance factor F D = 0.023(800) 0616 = 1.413 

Gradient factor F G = 0.877e [0046(6)] = 1.156 

Pay gravel transportation cost = (0.165 + 0.344) x 1.413 x 1.156 = $0.831/LCY 

Annual front-end loader operating cost = $0.831/LCY x 150,000 LCY/a 



$124,650 



Processing— conveyors (p. 59) 

70 yd 3 /h 

Equipment Y E = 0.218(70)-°- 561 

Parts $0,020 x 0.72 x 1.005 

Electricity $0,020 x 0.24 x 1.029 

Lubrication $0,020 x 0.04 x 0.991 

Labor Y L = 0.250(70)-°- 702 

Labor $0,013 x 1.00 x 1.025 

Conveyor operating cost = (0.020 + 0.013) = $0.033/yd 3 

Annual conveyor operating cost = $0.033/yd 3 x 105,000 yd 3 /a 



$0.020/yd 3 

$0,014 
0.005 
0.001 



$0,020 

$0.013/yd 3 

$0,013 



$3,465 



Processing— feed hoppers (p. 60) 

100 LCY/h total 

Equipment Y E = 0.033(100r - 344 = 

Parts $0,007 x 0.88 x 1.005 = 

Electricity $0,007 x 0.06 x 1.029 = 

Lubrication $0,007 x 0.06 x 0.991 = 

Labor Y L = 0.017(100)- °- 295 = 

Labor $0,004 x 1.00 x 1.025 = 

Feed hopper operating cost = (0.007 + 0.004) = $0.011/LCY 

Annual feed hopper operating cost = $0.011/LCY x 150,000 LCY/a 



$0.007/LCY 

$0,006 
0.0004 
0.0004 



$0,007 
$0.004/LCY 
$0,004 



$1,650 



90 



Processing— rougher jig (p. 61) 

20 ydVh 

Equipment Y E = 0.113(20)-°- 328 = 

Parts $0,042 x 0.40 x 1.005 = 

Electricity $0,042 x 0.34 x 1.029 = 

Lubrication $0,042 x 0.26 x 0.991 = 

Supplies Y s = 0.002(20r 0184 = 

Industrial materials $0,001 x 1.00 x 1.003 = 

Labor Y L = 3.508(20)" 1268 = 

Labor $0,079 x 1.00 x 1.025 = 

Rougher service factor F R = 

Rougher jig operating cost = (0.043 + 0.001 + 0.081) x 0.344 = $0.043/yd 3 

Annual rougher jig operating cost = $0.043/yd 3 x 30,000 yd 3 /a . . . . 



$0.042/yd 3 

$0,017 
0.015 
0.011 



$0,043 
$0.001/yd 3 
$0,001 
$0.079/yd 3 
$0,081 
0.344 



$1,290 



Processing— cleaner jigs (p. 61) 

2 at 5 yd 3 /h 

Equipment Y E = 0.113(5)-°- 328 

Parts $0,067 x 0.40 x 1.005 

Electricity $0,067 x 0.34 x 1.029 

Lubrication $0,067 x 0.26 x 0.991 

Supplies Y s = 0.002(5)-° 184 

Industrial materials $0,001 x 1.00 x 1.003 

Labor Y L = 3.508(5)" 1268 

Labor $0,456 x 1.00 x 1.025 

Cleaner jig operating cost = (0.067 + 0.001 + 0.467) = $0.535/yd 3 
Annual cleaner jig operating cost = $0.535/yd 3 x 15,000 yd 3 /a. 



$0.067/yd 3 

$0,027 
0.023 
0.017 



$0,067 

$0.001/yd 3 

$0,001 

$0.456/yd 3 

$0,467 



$8,025 



91 



Processing— final jig (p. 61) 

0.2 yd 3 /h 

Equipment Y E = 0.113(0.2)-°- 328 

Parts $0,192 x 0.40 x 1.005 

Electricity $0,192 x 0.34 x 1.029 

Lubrication $0,192 x 0.26 x 0.991 

Supplies Y s = 0.002(0.2)-° 184 

Industrial materials $0,003 x 1.00 x 1.003 

Labor Y L = 3.508(0.2)" 1268 

Labor $26,999 x 1.00 x 1.025 

Final jig operating cost = (0.193 + 0.003 + 27.674) = $27.870/yd 3 
Annual final jig operating cost = $27.870/yd 3 x 300 yd 3 /a . . . 



$0.192/yd 3 

$0,077 
0.067 
0.049 



$0,193 

$0.003/yd 3 

$0,003 
$26.999/yd 3 
$27,674 



$8,361 



Processing— sluices (p. 62) 

50 yd 3 /h 

Labor Y L = 0.377(50)-°- 636 

Labor $0,031 x 1.00 x 1.025 

Sluice operating cost = $0.032/yd 3 

Annual sluice operating cost - $0.032/yd 3 x 75,000 yd 3 /a 



$0.031/yd 3 
$0,032 



$2,400 



92 



Processing— Sluices (p. 62) 

20 ydVh 

Labor Y L = 0.377(20)-°- 636 

Labor $0,056 x 1.00 x 1.025 

Sluice operating cost = $0.057/yd 3 

Annual sluice operating cost = $0.057/yd 3 x 30,000 yd7a 



$0.056/yd 3 
$0,057 



$1,710 



Processing— Tailings removal— bulldozers (p. 65) 

100 LCY/h 

400-ft average haul distance 

-8% average haul gradient 

Equipment Y E = 0.993(100)-°- 430 = $0.137/LCY 

Parts $0,137 x 0.47 x 1.005 = $0,065 

Fuel and lubrication $0,137 x 0.53 x 0.991 = 0.072 

$0,137 

Labor Y L = 14.01(100)-°- 945 = $0.180/LCY 

Labor $0,180 x 1.00 x 1.025 = $0,185 

Distance factor F D = 0.00581(400)° 904 = 1.307 

Gradient factor F G = 1.041e [0015( - 8)] = 0.923 

Used equipment factor U e = 1.206(100)-° 013 = 1.136 

Uj = 0.967(100) 0015 = 1.036 

Tailings removal cost = [(0.137 x 1.136) + (0.185 x 1.036)] x 1.307 x 0.923 = $0.419/LCY 

Annual bulldozer operating cost = $0.419/LCY x 150,000 LCY/a 



$62,850 



Processing— trommels (p. 70) 

100 yd 3 /h 

Equipment Y E = 0.217(100r°- 403 

Parts $0,034 x 0.63 x 1.005 

Electricity $0,034 x 0.26 x 1.029 

Lubrication $0,034 X 0.11 x 0.991 

Labor Y L = 0.129(100)-°- 429 

Labor $0,018 x 1.00 x 1.025 

Trommel operating cost = ($0,035 + $0,018) = $0.053/yd 3 
Annual trommel operating cost = $0.053/yd 3 x 150,000 yd 3 /a 



$0.034/yd 3 

$0,022 
0.009 
0.004 



$0,035 

$0.018/yd 3 

$0,018 



$7,950 



93 



Supplemental— housing (p. 72) 

100 LCY/h pay gravel 
250 LCY/h overburden 
350 LCY/h total 

Supplies Y s = 1.445(350)-°- 583 

Fuel $0,047 x 0.05 x 0.991 

Industrial materials $0,047 x 0.95 x 1.003 



= $0.047/LCY 

$0,002 
0.045 



$0,047 



Housing operating cost = $0.047/LCY 

Annual housing operating cost = $0.047/LCY x 525,000 LCY/a 



$24,675 



Supplemental— lost time and general services (p. 74) 

100-yd 3 /h mill feed 

Equipment Y E = 0.142(100) 0004 = $0.145/LCY 

Fuel $0,145 x 0.53 x 0.991 = $0,076 

Parts $0,145 x 0.47 x 1.005 = 0.068 

$0,144 

Labor Y L = 2.673(100)-°' 524 = $0.239/LCY 

Labor $0,239 x 1.00 x 1.025 = $0,245 

Lost time and general service cost = ($0,144 + $0,245) = $0.389/LCY 

Annual lost time and general service cost = $0.389/LCY x 675,000 LCY/a 



$262,575 



Supplemental— pumps (p. 75) 

100 ydVh mill feed 
1,163 gpm 
80-ft head 

Equipment Y E = 0.007(1, 163) 0713 = 

Fuel and lubrication $1,074 x 0.59 x 0.991 = 

Parts $1,074 x 0.41 x 1.005 = 

Labor Y L = 0.004(1163) - 867 = 

Labor $1,819 x 1.00 x 1.025 = 

Head factor H e = 0.09K80) - 735 = 

H, = 0.054(80) 0893 = 

Pump operating cost = [($1,071 x 2.279) + ($1,864 x 2.739)] = $7.546/h 

Annual pump operating cost = $7.546/h x 1,500 h/a 



$1.074/h 

$0,628 
0.443 



$1,071 

$1.819/h 

$1,864 

2.279 
2.739 



$11,319 



** 



788 



4b'3 



94 



OPERATING COST SUMMARY FORM 

Item Annual cost 

Overburden removal: 

Bulldozers $ 

Draglines 

Front-end loaders 

Rear-dump trucks 151,125 

Scrapers 

Mining: 

Backhoes 73,650 

Bulldozers 

Draglines 

Front-end loaders 124,650 

Rear-dump trucks 

Scrapers 

Processing: 

Conveyors 3,465 

Feed hoppers 1 ,650 

Jig concentrators 1 7,676 

Sluices 4,110 

Spiral concentrators 

Table concentrators 

Tailings removal: 

Bulldozers 62,850 

Draglines 

Front-end loaders 

Rear-dump trucks 

Scrapers 

Trommels 7,950 

Vibrating screens 

Supplemental: 

Employee housing 24,675 

Lost time and general services 262,575 

Pumps 11,319 

Subtotal 745,695 

Contingency (1 0%) 74,570 

Total 820,265 

Cost per cubic yard pay gravel = total annual cost divided by pay gravel mined per year. 

$820,265/150,000 LCY/a = $5.47/LCY 
Final cost per cubic yard pay gravel $5.47 

Figure A-3.— Operating cost summary form completed for example estimation. 




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